• Functions and hormones of Pineal Gland

Pineal Gland: Functions and Hormones

The pineal gland is a small, pea-shaped endocrine gland located in the brain, between the two hemispheres, in a groove where the two halves of the thalamus join. It plays a crucial role in regulating biological rhythms and certain endocrine functions.

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Functions of the Pineal Gland

1. Regulation of Circadian Rhythms:
   • The pineal gland regulates the body’s internal biological clock by controlling sleep-wake cycles.
   • It synchronizes circadian rhythms with external light-dark cycles using signals from the suprachiasmatic nucleus (SCN) of the hypothalamus.
2. Production of Melatonin:
   • Secretes the hormone melatonin, which controls sleep and wakefulness.
   • Melatonin levels are higher at night, promoting sleep, and lower during the day, maintaining wakefulness.
3. Influence on Reproductive Hormones:
   • Melatonin affects the secretion of gonadotropins (luteinizing hormone and follicle-stimulating hormone) from the anterior pituitary.
   • Plays a role in regulating puberty onset and seasonal reproductive cycles in animals.
4. Antioxidant Properties:
   • Melatonin acts as a powerful antioxidant, protecting cells from oxidative stress and damage caused by free radicals.
5. Immune System Regulation:
   • The pineal gland indirectly influences the immune system by modulating immune responses through melatonin.
6. Mood Regulation:
   • Melatonin interacts with neurotransmitters like serotonin, influencing mood and possibly playing a role in conditions like seasonal affective disorder (SAD).

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Hormones Secreted by the Pineal Gland

1. Melatonin:

• Primary Hormone: Produced from serotonin, a neurotransmitter derived from tryptophan.
• Secretion Pattern:
  • Increased secretion during darkness (night).
  • Decreased secretion in response to light (daytime).
• Functions:
  • Regulates sleep-wake cycles.
  • Modulates seasonal biological rhythms (e.g., breeding cycles in animals).
  • Protects cells from oxidative stress (antioxidant role).
  • Regulates body temperature and blood pressure.

2. Serotonin (Precursor of Melatonin):

• While not a direct product of the pineal gland, serotonin is a precursor for melatonin synthesis.
• Plays a role in mood regulation and may influence melatonin’s effects on the sleep-wake cycle.

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Disorders Associated with Pineal Gland Dysfunction

1. Sleep Disorders:
   • Imbalances in melatonin production can lead to insomnia, delayed sleep phase syndrome, or irregular sleep-wake cycles.
2. Seasonal Affective Disorder (SAD):
   • A type of depression linked to reduced melatonin and serotonin activity during shorter daylight hours in winter.
3. Delayed Puberty:
   • Overproduction of melatonin can suppress gonadotropin secretion, potentially delaying puberty.
4. Pineal Gland Tumors:
   • Can disrupt melatonin production and interfere with circadian rhythms or lead to other neurological symptoms.

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Regulation of Pineal Gland Activity

• Light Exposure:
  • Light detected by the retina is transmitted to the pineal gland through the retinohypothalamic tract and the suprachiasmatic nucleus (SCN).
  • Light inhibits melatonin production, while darkness stimulates it.
• Neurotransmitters:
  • The pineal gland receives signals from the sympathetic nervous system, which regulates melatonin synthesis.

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Summary

• The pineal gland is a critical regulator of the body’s biological clock, primarily through its production of melatonin.
• It influences sleep, mood, reproductive cycles, and immune function.
• Dysfunction of the pineal gland can lead to sleep disorders, mood disturbances, and other systemic effects.

• Pituitary gland,

Pituitary Gland: Overview

The pituitary gland, often referred to as the master gland, is a pea-shaped endocrine gland located at the base of the brain, below the hypothalamus, within a bony cavity called the sella turcica. It plays a central role in regulating other endocrine glands and maintaining homeostasis by secreting various hormones.

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Structure of the Pituitary Gland

The pituitary gland is divided into two main parts:

1. Anterior Pituitary (Adenohypophysis):
   • Constitutes about 75% of the gland.
   • Regulated by the hypothalamus via releasing and inhibiting hormones.
2. Posterior Pituitary (Neurohypophysis):
   • Constitutes about 25% of the gland.
   • Stores and releases hormones produced by the hypothalamus.

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Hormones Secreted by the Pituitary Gland

A. Anterior Pituitary Hormones

1. Growth Hormone (GH):
   • Stimulates growth, cell reproduction, and regeneration.
   • Acts on bones, muscles, and liver.
   • Disorders:
     • Excess: Gigantism (in children) or Acromegaly (in adults).
     • Deficiency: Dwarfism.
2. Thyroid-Stimulating Hormone (TSH):
   • Stimulates the thyroid gland to produce thyroxine (T4) and triiodothyronine (T3).
   • Disorders:
     • Excess: Hyperthyroidism.
     • Deficiency: Hypothyroidism.
3. Adrenocorticotropic Hormone (ACTH):
   • Stimulates the adrenal cortex to produce cortisol, aldosterone, and androgens.
   • Disorders:
     • Excess: Cushing’s syndrome.
     • Deficiency: Adrenal insufficiency.
4. Prolactin (PRL):
   • Promotes milk production in the mammary glands.
   • Disorders:
     • Excess: Galactorrhea, menstrual irregularities.
     • Deficiency: Reduced milk production in nursing mothers.
5. Follicle-Stimulating Hormone (FSH):
   • In women: Stimulates ovarian follicle maturation and estrogen production.
   • In men: Stimulates sperm production.
6. Luteinizing Hormone (LH):
   • In women: Triggers ovulation and stimulates the production of progesterone.
   • In men: Stimulates testosterone production by the testes.
7. Melanocyte-Stimulating Hormone (MSH):
   • Regulates skin pigmentation by stimulating melanin production.

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B. Posterior Pituitary Hormones

1. Antidiuretic Hormone (ADH) (Vasopressin):
   • Promotes water reabsorption in the kidneys, reducing urine output.
   • Disorders:
     • Deficiency: Diabetes insipidus.
     • Excess: Syndrome of inappropriate ADH secretion (SIADH).
2. Oxytocin:
   • Stimulates uterine contractions during childbirth.
   • Promotes milk ejection during breastfeeding.
   • Plays a role in bonding and social behaviors.

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Functions of the Pituitary Gland

1. Growth and Development:
   • Regulates overall growth through GH.
   • Coordinates sexual maturation and reproductive cycles via FSH and LH.
2. Metabolic Regulation:
   • Controls thyroid function (TSH) and adrenal activity (ACTH), affecting metabolism and stress response.
3. Water and Electrolyte Balance:
   • Maintains fluid homeostasis through ADH.
4. Reproduction:
   • Regulates ovarian and testicular function (FSH, LH) and supports lactation (Prolactin).
5. Stress Response:
   • Stimulates cortisol production (ACTH) to help the body adapt to stress.

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Disorders of the Pituitary Gland

1. Hyperpituitarism:
   • Overproduction of pituitary hormones.
   • Examples: Acromegaly, gigantism, Cushing’s disease.
2. Hypopituitarism:
   • Underproduction of pituitary hormones.
   • Causes: Tumors, trauma, or infarction.
3. Pituitary Adenomas:
   • Benign tumors affecting hormone secretion.

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Regulation of the Pituitary Gland

• The pituitary gland is controlled by the hypothalamus, which secretes releasing and inhibiting hormones.
• Examples:
  • Thyrotropin-releasing hormone (TRH) stimulates TSH secretion.
  • Corticotropin-releasing hormone (CRH) stimulates ACTH secretion.

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• Thyroid

Thyroid Gland: Overview

The thyroid gland is a butterfly-shaped endocrine gland located in the neck, just below the larynx (voice box) and in front of the trachea. It plays a critical role in regulating metabolism, growth, and development by producing thyroid hormones.

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Structure of the Thyroid Gland

• Lobes: The thyroid consists of two lobes (right and left) connected by a narrow band of tissue called the isthmus.
• Microscopic Structure:
  • Composed of follicles filled with colloid, which stores precursors of thyroid hormones.
  • The follicular cells produce hormones T3 (triiodothyronine) and T4 (thyroxine).
  • Parafollicular cells (C cells) produce calcitonin, a hormone involved in calcium regulation.

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Hormones Secreted by the Thyroid Gland

1. Thyroxine (T4):
   • Contains four iodine atoms.
   • Primary form of hormone produced by the thyroid.
   • Less active than T3 but serves as a precursor.
2. Triiodothyronine (T3):
   • Contains three iodine atoms.
   • More biologically active than T4.
   • T4 is converted into T3 in peripheral tissues.
3. Calcitonin:
   • Secreted by parafollicular (C) cells.
   • Regulates calcium levels in the blood by reducing blood calcium levels:
     • Inhibits bone resorption by osteoclasts.
     • Promotes calcium deposition in bones.

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Functions of Thyroid Hormones (T3 and T4)

1. Regulation of Metabolism:
   • Increases the basal metabolic rate (BMR).
   • Enhances oxygen consumption and energy production in cells.
2. Thermoregulation:
   • Maintains body temperature by increasing heat production.
3. Growth and Development:
   • Essential for normal growth, especially of the bones and brain in children.
   • Promotes protein synthesis.
4. Cardiovascular Effects:
   • Increases heart rate and cardiac output.
   • Enhances sensitivity to catecholamines (e.g., adrenaline).
5. Nervous System Regulation:
   • Affects alertness, reflexes, and cognitive function.
   • Plays a critical role in fetal and neonatal brain development.
6. Reproductive Function:
   • Helps maintain normal menstrual cycles and fertility.
7. Lipid and Carbohydrate Metabolism:
   • Promotes fat breakdown (lipolysis) and glucose utilization.

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Regulation of Thyroid Hormone Secretion

• Controlled by the Hypothalamus-Pituitary-Thyroid (HPT) Axis:
  1. The hypothalamus secretes thyrotropin-releasing hormone (TRH).
  2. TRH stimulates the anterior pituitary to release thyroid-stimulating hormone (TSH).
  3. TSH stimulates the thyroid gland to produce and release T3 and T4.
  4. A negative feedback loop ensures that high levels of T3 and T4 inhibit further release of TRH and TSH.

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Disorders of the Thyroid Gland

1. Hypothyroidism:
   • Cause: Insufficient production of thyroid hormones.
   • Symptoms:
     • Fatigue, weight gain, cold intolerance.
     • Dry skin, hair thinning, constipation.
     • Depression, slowed heart rate.
   • Examples:
     • Hashimoto’s Thyroiditis: Autoimmune destruction of the thyroid.
     • Iodine Deficiency: Common in areas with low dietary iodine.
   • Treatment: Thyroid hormone replacement (e.g., levothyroxine).
2. Hyperthyroidism:
   • Cause: Excessive production of thyroid hormones.
   • Symptoms:
     • Weight loss, heat intolerance, rapid heartbeat.
     • Tremors, nervousness, sweating.
     • Bulging eyes (exophthalmos) in Graves’ disease.
   • Examples:
     • Graves’ Disease: Autoimmune condition causing overactivity.
     • Toxic Nodular Goiter.
   • Treatment: Antithyroid drugs, radioactive iodine, or surgery.
3. Goiter:
   • Enlargement of the thyroid gland.
   • Cause:
     • Iodine deficiency (endemic goiter).
     • Thyroid dysfunction (hyperthyroidism or hypothyroidism).
4. Thyroid Nodules and Cancer:
   • Nodules can be benign or malignant.
   • Requires evaluation via imaging and biopsy.

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Clinical Importance of Thyroid Function Tests

1. TSH Test:
   • Primary screening test for thyroid dysfunction.
   • High TSH: Indicates hypothyroidism.
   • Low TSH: Indicates hyperthyroidism.
2. Free T3 and T4 Tests:
   • Measure active thyroid hormones in the blood.
3. Thyroid Antibodies:
   • Detect autoimmune thyroid conditions like Hashimoto’s or Graves’ disease.
4. Thyroid Ultrasound:
   • Evaluates the size, structure, and presence of nodules.

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• Parathyroid

Parathyroid Gland: Overview

The parathyroid glands are four small, oval-shaped endocrine glands located on the posterior surface of the thyroid gland. Despite their proximity to the thyroid, they are distinct in structure and function. The parathyroid glands play a critical role in maintaining calcium homeostasis in the body.

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Structure and Location

• Typically four glands: Two on each lobe of the thyroid gland.
• Variations in number and location may occur (e.g., ectopic parathyroid glands).

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Hormone Secreted by the Parathyroid Glands

Parathyroid Hormone (PTH):

• Primary hormone secreted by the chief cells of the parathyroid glands.
• Regulates calcium and phosphate levels in the blood and bone.

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Functions of the Parathyroid Glands (via PTH)

1. Regulation of Blood Calcium Levels:
   • PTH increases calcium levels in the blood when they fall below normal.
   • Target organs:
     • Bones:
       • Stimulates osteoclast activity, leading to bone resorption and release of calcium into the bloodstream.
     • Kidneys:
       • Enhances calcium reabsorption in the renal tubules, reducing calcium loss in urine.
       • Promotes the excretion of phosphate, maintaining a balance between calcium and phosphate.
     • Intestines:
       • Indirectly increases calcium absorption by stimulating the production of active Vitamin D (calcitriol) in the kidneys.
2. Phosphate Regulation:
   • Decreases phosphate reabsorption in the kidneys, leading to increased phosphate excretion.
3. Activation of Vitamin D:
   • PTH stimulates the kidneys to convert inactive Vitamin D (calcidiol) into active Vitamin D (calcitriol).
   • Calcitriol enhances calcium and phosphate absorption in the intestines.

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Regulation of Parathyroid Hormone Secretion

• Negative Feedback Mechanism:
  • Low blood calcium: Stimulates PTH secretion.
  • High blood calcium: Inhibits PTH secretion.
• Calcium-Sensing Receptors (CaSR):
  • Located on the parathyroid cells.
  • Detect blood calcium levels and regulate PTH release.

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Disorders of the Parathyroid Glands

1. Hyperparathyroidism:
   • Primary Hyperparathyroidism:
     • Cause: Overproduction of PTH due to a parathyroid adenoma or hyperplasia.
     • Effects:
       • Hypercalcemia (high blood calcium levels).
       • Symptoms: Kidney stones, bone pain (osteoporosis), abdominal pain, and fatigue.
   • Secondary Hyperparathyroidism:
     • Cause: Chronic hypocalcemia, often due to kidney failure or Vitamin D deficiency.
     • PTH is elevated as a compensatory response.
2. Hypoparathyroidism:
   • Cause: Underproduction of PTH, often due to surgical removal of the parathyroid glands, autoimmune conditions, or genetic disorders.
   • Effects:
     • Hypocalcemia (low blood calcium levels).
     • Symptoms: Muscle spasms (tetany), numbness, seizures, and cardiac arrhythmias.
3. Pseudohypoparathyroidism:
   • A condition where the body is resistant to the effects of PTH, leading to hypocalcemia despite high PTH levels.

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Clinical Importance

1. Calcium Homeostasis:
   • Parathyroid glands are essential for maintaining stable blood calcium levels, critical for nerve transmission, muscle contraction, and blood clotting.
2. Diagnostic Tests:
   • Serum Calcium and Phosphate Levels:
     • High PTH: Associated with hypercalcemia and hypophosphatemia.
     • Low PTH: Associated with hypocalcemia and hyperphosphatemia.
   • PTH Levels:
     • Measured directly to diagnose parathyroid disorders.
   • Bone Density Scans:
     • To assess bone health in hyperparathyroidism.

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• Thymus,

Thymus Gland: Overview

The thymus gland is a specialized primary lymphoid organ of the immune system. It plays a crucial role in the development and maturation of T-lymphocytes (T-cells), which are essential for adaptive immunity. The thymus is most active during childhood and begins to shrink (atrophy) after puberty.

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Location and Structure

• Location:
  • Situated in the mediastinum, behind the sternum and in front of the heart.
• Structure:
  • Encapsulated, bilobed organ.
  • Divided into:
    • Cortex: Outer region rich in immature T-cells (thymocytes).
    • Medulla: Inner region containing mature T-cells and epithelial cells.

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Functions of the Thymus

1. T-Cell Maturation:
   • Immature T-cells (thymocytes) from the bone marrow migrate to the thymus.
   • Here, they undergo differentiation and maturation to become functional T-lymphocytes.
2. Positive and Negative Selection:
   • Positive Selection:
     • Ensures T-cells can recognize self-major histocompatibility complex (MHC) molecules.
   • Negative Selection:
     • Eliminates self-reactive T-cells to prevent autoimmune responses.
3. Hormone Secretion:
   • Produces hormones like thymosins, thymopoietin, and thymulin, which:
     • Regulate T-cell development.
     • Enhance the immune response.
4. Immune System Regulation:
   • Facilitates the establishment of self-tolerance to prevent the immune system from attacking the body’s own tissues.
5. Lymphocyte Export:
   • Mature T-cells are exported to peripheral lymphoid tissues (e.g., lymph nodes, spleen) to perform immune surveillance and defense.

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Hormones Secreted by the Thymus

1. Thymosin:
   • Stimulates the development of T-cells and enhances immune function.
2. Thymopoietin:
   • Promotes T-cell differentiation and helps maintain the structural integrity of the thymus.
3. Thymulin:
   • Influences T-cell differentiation and enhances the immune response in coordination with other immune mediators.

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Changes in the Thymus Over Time

• Active During Childhood:
  • Largest and most active during infancy and early childhood.
• Involution After Puberty:
  • Shrinks in size and becomes largely replaced by fatty tissue.
  • T-cell production declines but remains functional throughout life.

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Clinical Significance

1. Thymus Disorders:
   • DiGeorge Syndrome:
     • A congenital condition where the thymus fails to develop properly, leading to severe immunodeficiency.
   • Thymoma:
     • A tumor of the thymus, often associated with autoimmune diseases like myasthenia gravis.
   • Thymic Hyperplasia:
     • Enlargement of the thymus, which can also be linked to autoimmune conditions.
2. Autoimmune Diseases:
   • Dysfunctional negative selection in the thymus may result in autoimmune diseases due to the survival of self-reactive T-cells.
3. Role in Immunosenescence:
   • With age, thymus involution contributes to a decline in immune function, increasing susceptibility to infections and cancer.

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• Pancreas and Adrenal glands.

Pancreas and Adrenal Glands

Both the pancreas and adrenal glands are vital endocrine organs, each with distinct roles in regulating metabolism, energy balance, and stress response.

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1. Pancreas

Overview:

The pancreas is a gland located behind the stomach, functioning as both an exocrine (digestive enzymes) and endocrine (hormonal regulation) organ.

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Structure:

1. Exocrine Component:
   • Acinar cells secrete digestive enzymes (amylase, lipase, proteases) into the duodenum via pancreatic ducts.
2. Endocrine Component:
   • Islets of Langerhans are clusters of hormone-secreting cells:
     • Alpha cells: Produce glucagon.
     • Beta cells: Produce insulin.
     • Delta cells: Produce somatostatin.
     • PP cells (F cells): Produce pancreatic polypeptide.

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Hormones Secreted by the Pancreas:

1. Insulin:
   • Secreted by beta cells in response to high blood glucose levels.
   • Functions:
     • Promotes glucose uptake by cells.
     • Enhances glycogen synthesis in the liver and muscles.
     • Stimulates fat storage and protein synthesis.
     • Disorders: Deficiency causes diabetes mellitus (Type 1 or Type 2).
2. Glucagon:
   • Secreted by alpha cells when blood glucose is low.
   • Functions:
     • Stimulates glycogen breakdown (glycogenolysis) in the liver.
     • Promotes gluconeogenesis (synthesis of glucose from non-carbohydrate sources).
     • Raises blood glucose levels.
3. Somatostatin:
   • Secreted by delta cells.
   • Functions:
     • Inhibits secretion of insulin and glucagon.
     • Reduces gastric motility and hormone release.
4. Pancreatic Polypeptide:
   • Secreted by PP cells.
   • Functions:
     • Regulates pancreatic secretion and gastrointestinal motility.

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Disorders of the Pancreas:

1. Diabetes Mellitus:
   • Type 1: Autoimmune destruction of beta cells → Insulin deficiency.
   • Type 2: Insulin resistance → Inefficient glucose uptake.
2. Hypoglycemia:
   • Excess insulin secretion leads to low blood glucose levels.
3. Pancreatitis:
   • Inflammation of the pancreas, often due to alcohol or gallstones.

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2. Adrenal Glands

Overview:

The adrenal glands are paired, triangular-shaped organs located on top of the kidneys. They consist of two distinct regions with different functions:

1. Adrenal Cortex (outer layer): Produces steroid hormones.
2. Adrenal Medulla (inner core): Produces catecholamines.

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Adrenal Cortex Hormones:

1. Mineralocorticoids (e.g., Aldosterone):
   • Regulates electrolyte balance and blood pressure.
   • Functions:
     • Increases sodium reabsorption and potassium excretion in the kidneys.
     • Promotes water retention, increasing blood volume and pressure.
   • Disorders:
     • Excess: Hyperaldosteronism (high blood pressure, hypokalemia).
     • Deficiency: Addison’s disease.
2. Glucocorticoids (e.g., Cortisol):
   • Helps the body respond to stress.
   • Functions:
     • Increases blood glucose via gluconeogenesis.
     • Suppresses inflammation and immune response.
     • Promotes fat and protein metabolism.
   • Disorders:
     • Excess: Cushing’s syndrome (weight gain, hypertension, muscle weakness).
     • Deficiency: Addison’s disease (fatigue, low blood pressure, hypoglycemia).
3. Androgens:
   • Weak male sex hormones (e.g., dehydroepiandrosterone [DHEA]).
   • Functions:
     • Contribute to secondary sexual characteristics.
     • Converted to testosterone or estrogen in peripheral tissues.

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Adrenal Medulla Hormones:

1. Epinephrine (Adrenaline):
   • Secreted during the “fight or flight” response.
   • Functions:
     • Increases heart rate and blood pressure.
     • Dilates airways.
     • Mobilizes energy by promoting glycogen breakdown.
2. Norepinephrine (Noradrenaline):
   • Works with epinephrine to enhance stress response.
   • Functions:
     • Constricts blood vessels, increasing blood pressure.
     • Maintains vascular tone during stress.

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Disorders of the Adrenal Glands:

1. Addison’s Disease:
   • Adrenal insufficiency leading to low cortisol and aldosterone levels.
   • Symptoms: Fatigue, weight loss, hyperpigmentation, low blood pressure.
2. Cushing’s Syndrome:
   • Excess cortisol production.
   • Symptoms: Central obesity, moon face, hypertension, muscle weakness.
3. Pheochromocytoma:
   • Tumor of the adrenal medulla causing excessive catecholamine secretion.
   • Symptoms: Palpitations, sweating, high blood pressure.
4. Congenital Adrenal Hyperplasia (CAH):
   • Genetic disorder affecting cortisol and aldosterone synthesis.

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Comparison of Pancreas and Adrenal Glands

Feature	Pancreas	Adrenal Glands
Primary Function	Regulates blood sugar levels.	Responds to stress and maintains electrolyte balance.
Main Hormones	Insulin, glucagon, somatostatin	Cortisol, aldosterone, epinephrine, norepinephrine
Location	Behind the stomach	Above the kidneys

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• Other hormones

Other Hormones and Their Functions

In addition to the hormones produced by the pancreas, adrenal glands, thyroid, and pituitary gland, the human body secretes a wide range of hormones from various other glands and tissues. Here’s an overview:

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1. Hypothalamus Hormones

The hypothalamus regulates the endocrine system by controlling the pituitary gland.

1. Thyrotropin-Releasing Hormone (TRH):
   • Stimulates the release of thyroid-stimulating hormone (TSH) from the anterior pituitary.
2. Corticotropin-Releasing Hormone (CRH):
   • Stimulates the release of adrenocorticotropic hormone (ACTH).
3. Gonadotropin-Releasing Hormone (GnRH):
   • Stimulates the release of luteinizing hormone (LH) and follicle-stimulating hormone (FSH).
4. Growth Hormone-Releasing Hormone (GHRH):
   • Stimulates the release of growth hormone (GH).
5. Somatostatin:
   • Inhibits the release of GH and TSH.
6. Dopamine (Prolactin-Inhibiting Hormone):
   • Inhibits the release of prolactin.

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2. Pineal Gland Hormone

1. Melatonin:
   • Regulates circadian rhythms (sleep-wake cycle).
   • Influences seasonal biological rhythms.

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3. Parathyroid Gland Hormone

1. Parathyroid Hormone (PTH):
   • Regulates calcium and phosphate balance by increasing blood calcium levels.

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4. Hormones of the Gonads

A. Ovaries (Female):

1. Estrogen:
   • Regulates female reproductive development, menstrual cycle, and secondary sexual characteristics.
2. Progesterone:
   • Prepares the uterus for pregnancy and supports early fetal development.
3. Inhibin:
   • Inhibits FSH secretion.

B. Testes (Male):

1. Testosterone:
   • Regulates male reproductive development, spermatogenesis, and secondary sexual characteristics.
2. Inhibin:
   • Inhibits FSH secretion.

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5. Hormones of the Placenta (During Pregnancy)

1. Human Chorionic Gonadotropin (hCG):
   • Maintains the corpus luteum and supports progesterone secretion during early pregnancy.
2. Human Placental Lactogen (hPL):
   • Prepares the breasts for lactation.
   • Regulates maternal glucose and fat metabolism to support fetal growth.
3. Relaxin:
   • Relaxes pelvic ligaments and softens the cervix for childbirth.
4. Estrogen and Progesterone:
   • Produced by the placenta to maintain pregnancy.

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6. Gastrointestinal Hormones

1. Gastrin:
   • Stimulates the secretion of gastric acid (HCl) in the stomach.
2. Secretin:
   • Stimulates the pancreas to release bicarbonate to neutralize stomach acid.
3. Cholecystokinin (CCK):
   • Stimulates the release of digestive enzymes from the pancreas and bile from the gallbladder.
4. Ghrelin:
   • Stimulates appetite and promotes food intake.
5. Motilin:
   • Regulates gastrointestinal motility during fasting.

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7. Kidney Hormones

1. Erythropoietin (EPO):
   • Stimulates red blood cell production in the bone marrow.
2. Renin:
   • Part of the renin-angiotensin-aldosterone system (RAAS) to regulate blood pressure and fluid balance.
3. Calcitriol (Active Vitamin D):
   • Enhances calcium and phosphate absorption in the intestines.

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8. Hormones of the Heart

1. Atrial Natriuretic Peptide (ANP):
   • Reduces blood pressure by promoting sodium and water excretion in the kidneys.

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9. Hormones of Adipose Tissue

1. Leptin:
   • Suppresses appetite and regulates energy balance.
2. Adiponectin:
   • Enhances insulin sensitivity and has anti-inflammatory effects.

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10. Other Notable Hormones

1. Prostaglandins:
   • Local hormones with diverse roles in inflammation, blood flow, and uterine contractions.
2. Thymosin (from the Thymus):
   • Promotes T-cell development for immune function.
3. Eicosanoids:
   • Involved in immune responses, inflammation, and blood clotting.
4. Endothelins (from Endothelial Cells):
   • Regulate vascular tone and blood pressure.

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Summary Table of Hormone Sources

Source	Major Hormones
Hypothalamus	TRH, CRH, GnRH, GHRH, Somatostatin, Dopamine
Pituitary Gland	GH, TSH, ACTH, LH, FSH, Prolactin, ADH, Oxytocin
Thyroid	T3, T4, Calcitonin
Parathyroid	Parathyroid Hormone (PTH)
Adrenal Cortex	Cortisol, Aldosterone, Androgens
Adrenal Medulla	Epinephrine, Norepinephrine
Pancreas	Insulin, Glucagon, Somatostatin
Ovaries/Testes	Estrogen, Progesterone, Testosterone, Inhibin
Kidneys	Erythropoietin, Renin, Calcitriol
Gastrointestinal Tract	Gastrin, Secretin, CCK, Ghrelin
Pineal Gland	Melatonin
Heart	Atrial Natriuretic Peptide (ANP)
Placenta	hCG, hPL, Relaxin, Estrogen, Progesterone
Adipose Tissue	Leptin, Adiponectin

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• Alterations in disease

Alterations in Disease: Hormonal and Systemic Changes

Alterations in the body caused by disease often disrupt normal physiological functions, including hormonal balance, metabolic processes, and immune responses. Here is a detailed look at common disease-related alterations:

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1. Hormonal Alterations in Disease

A. Endocrine Disorders:

1. Hyperthyroidism (e.g., Graves’ Disease):
   • Cause: Excess thyroid hormone (T3, T4).
   • Alterations:
     • Increased metabolism → Weight loss, heat intolerance, and tachycardia.
     • Nervousness, tremors, and insomnia.
   • Clinical Features: Exophthalmos, goiter.
2. Hypothyroidism (e.g., Hashimoto’s Thyroiditis):
   • Cause: Deficiency of thyroid hormones.
   • Alterations:
     • Decreased metabolism → Weight gain, cold intolerance, and fatigue.
     • Bradycardia, constipation, and depression.
   • Clinical Features: Dry skin, hair loss, and myxedema.
3. Diabetes Mellitus:
   • Type 1: Autoimmune destruction of beta cells → Insulin deficiency.
   • Type 2: Insulin resistance in peripheral tissues.
   • Alterations:
     • Hyperglycemia, polyuria, polydipsia, and polyphagia.
     • Long-term complications: Neuropathy, nephropathy, retinopathy, cardiovascular disease.
4. Cushing’s Syndrome:
   • Cause: Excess cortisol production (e.g., adrenal tumor or exogenous steroids).
   • Alterations:
     • Hyperglycemia, central obesity, muscle weakness, and hypertension.
     • Thin skin, purple striae, and moon face.
5. Addison’s Disease:
   • Cause: Deficient cortisol and aldosterone production.
   • Alterations:
     • Hypoglycemia, hypotension, fatigue, and hyperpigmentation.
6. Polycystic Ovary Syndrome (PCOS):
   • Cause: Hormonal imbalance with increased androgens.
   • Alterations:
     • Menstrual irregularities, infertility, and hirsutism.
     • Insulin resistance and obesity.

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B. Hormonal Alterations in Stress and Trauma:

1. Acute Stress Response:
   • Increased cortisol, epinephrine, and norepinephrine.
   • Alterations:
     • Elevated heart rate, blood pressure, and glucose levels.
     • Enhanced immune suppression and energy mobilization.
2. Chronic Stress:
   • Sustained high cortisol levels.
   • Alterations:
     • Immune suppression, weight gain, and increased risk of hypertension.

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2. Metabolic Alterations in Disease

1. Acidosis and Alkalosis:
   • Metabolic Acidosis:
     • Cause: Diabetic ketoacidosis, renal failure.
     • Alteration: Low blood pH due to excess hydrogen ions or bicarbonate loss.
   • Metabolic Alkalosis:
     • Cause: Vomiting, excessive antacid use.
     • Alteration: Elevated blood pH due to bicarbonate accumulation.
2. Electrolyte Imbalances:
   • Hyperkalemia: Seen in renal failure; causes cardiac arrhythmias.
   • Hyponatremia: Seen in SIADH; causes confusion, seizures.
   • Hypercalcemia: Seen in hyperparathyroidism; causes fatigue, kidney stones.
3. Obesity:
   • Alterations:
     • Increased fat deposition → Insulin resistance, dyslipidemia.
     • Elevated inflammatory markers → Chronic low-grade inflammation.
4. Malnutrition:
   • Marasmus: Protein-calorie deficiency → Muscle wasting.
   • Kwashiorkor: Protein deficiency → Edema, fatty liver.

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3. Immune System Alterations in Disease

1. Autoimmune Diseases:
   • Systemic Lupus Erythematosus (SLE):
     • Immune system attacks multiple tissues → Inflammation, joint pain, kidney damage.
   • Rheumatoid Arthritis (RA):
     • Autoimmune attack on synovial joints → Swelling, pain, and deformity.
2. Immunodeficiency Disorders:
   • Primary (e.g., DiGeorge Syndrome): Congenital defect in T-cell production.
   • Secondary (e.g., HIV/AIDS): Destruction of CD4+ T-cells.
   • Alterations:
     • Increased susceptibility to infections.
     • Delayed wound healing.
3. Hypersensitivity Reactions:
   • Allergies (Type I Hypersensitivity):
     • IgE-mediated response to allergens → Rash, asthma, anaphylaxis.
   • Type IV Hypersensitivity:
     • Delayed T-cell-mediated response (e.g., poison ivy).

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4. Neurological Alterations in Disease

1. Stroke:
   • Alterations:
     • Ischemic: Reduced blood flow to the brain.
     • Hemorrhagic: Bleeding into the brain.
     • Symptoms: Paralysis, speech difficulties, and loss of consciousness.
2. Parkinson’s Disease:
   • Cause: Loss of dopamine-producing neurons.
   • Alterations:
     • Tremors, rigidity, and bradykinesia.
3. Alzheimer’s Disease:
   • Cause: Neurodegeneration due to amyloid plaques and tau tangles.
   • Alterations:
     • Memory loss, confusion, and cognitive decline.

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5. Cardiovascular Alterations in Disease

1. Hypertension:
   • Alterations:
     • Increased vascular resistance → Organ damage (heart, kidneys, brain).
     • Can lead to stroke, heart attack, or kidney failure.
2. Heart Failure:
   • Alterations:
     • Reduced cardiac output.
     • Fluid retention → Edema, dyspnea.
3. Atherosclerosis:
   • Alterations:
     • Plaque buildup in arteries → Reduced blood flow, ischemia.
     • Risk of heart attack and stroke.

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6. Alterations in Cancer

1. Cell Cycle Dysregulation:
   • Cancer cells evade normal cell cycle control.
   • Alterations:
     • Uncontrolled cell growth and division.
     • Resistance to apoptosis.
2. Metastasis:
   • Cancer cells spread to distant organs.
   • Alterations:
     • Invasion of surrounding tissues.
     • Formation of secondary tumors.

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Summary of Common Alterations in Disease

System Affected	Alterations	Examples
Endocrine	Hormonal imbalances	Diabetes, Cushing’s Syndrome
Metabolic	Acid-base disturbances, electrolyte imbalances	Acidosis, Hyperkalemia
Immune	Autoimmune responses, immunodeficiency	SLE, HIV/AIDS
Neurological	Neurodegeneration, ischemia	Parkinson’s, Stroke
Cardiovascular	Plaque buildup, reduced cardiac output	Atherosclerosis, Heart Failure
Cancer	Dysregulated cell growth, metastasis	Lung Cancer, Breast Cancer

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