Endocrine System Overview and Adrenal Glands

Endocrine System Overview

• Endocrine glands secrete hormones, regulating various bodily functions.
• The pituitary gland is the "master gland," controlling other endocrine glands.

Adrenal Glands

• Located near the kidneys.
• The adrenal cortex, controlled by ACTH from the pituitary, releases steroid hormones.
• ACTH release is triggered by stress (e.g., low blood sugar, low body temperature, shock).
• The adrenal medulla, part of the sympathetic nervous system, produces catecholamines (e.g., epinephrine, norepinephrine).

Adrenal Gland Hormones

• Mineralocorticoids (e.g., aldosterone): Regulate sodium and potassium balance in the kidneys.

  • Released in response to hyponatremia, hyperkalemia, and angiotensin II.
  • Increased secretion is called hyperaldosteronism (leading to hypokalemia and metabolic alkalosis).
  • Decreased secretion is called hypoaldosteronism (leading to hyperkalemia and metabolic acidosis).

• Glucocorticoids (e.g., cortisol): Vital for life, influencing various organs.

  • Cortisol's effects encompass metabolic processes, cardiovascular function, and suppressing the immune response.

• Androgens (e.g., DHEA): Play a role in sexual development.

• Catecholamines (e.g., epinephrine, norepinephrine): Released in response to stress, for quick responses (fight-or-flight).

  • These increase blood pressure and heart rate, increase metabolic rate, and cause glycogenolysis.

Glucocorticoid Effects

• Metabolic: Influence carbohydrate metabolism (anti-insulin effect), increasing blood sugar through gluconeogenesis; also decrease glucose utilization and increase protein catabolism.
• Metabolic: Affect lipolysis and fat redistribution.
• Cardiovascular: Maintaining normal cardiovascular function and responsiveness to catecholamines.
• Hematological: Decreases blood cells (except RBC and platelets), with anti-inflammatory effects on eosinophils, basophils, and lysosomes.
• Gastrointestinal: Increases gastric HCl secretion and decreased mucosal cell proliferation, (increases risk of ulcers).
• Psychological: Can cause euphoria, psychosis, depression and paranoia.
• Other: Increases lung surfactant in late pregnancy. Exerts an aldosterone-like effect.
• Circadian Rhythm: Cortisol levels follow a daily pattern, highest before waking and lowest at night.

Hypercortisolism (Cushing's Syndrome)

• Characterized by excessive cortisol production.
• Symptoms include moon face, buffalo hump, thin skin, muscle wasting, poor wound healing, osteoporosis.

Hypocortisolism (Addison's Disease)

• Characterized by insufficient cortisol production.
• Symptoms include fatigue, weakness, anorexia, weight loss, hyperpigmentation, postural dizziness, gastrointestinal problems, and decreased libido.

Antidiuretic Hormone (ADH)

• Regulates body water balance by influencing distal nephron permeability to water and increasing water reabsorption.
• Stimulates vascular smooth muscle contraction, increasing blood pressure (significant in hypovolemic shock).

Oxytocin

• A hypothalamus-derived hormone stored in the posterior pituitary.
• Released in response to nerve signals from stretch receptors in the cervix (during labour) and touch receptors in the nipples (milk ejection).
• Important in childbirth (labor and uterine contractions) and breastfeeding.
• Its release is enhanced by estrogen and antagonized by progesterone during pregnancy. Increased oxytocin sensitivity exists during late pregnancy.

Other important aspects of the endocrine system (from the last page of provided text)

• Pituitary gland is the master gland controlling many other endocrine glands' function involving growth hormone, prolactin, and ADH.
• Thyroid gland releases thyroxine, affecting metabolic rate.
• Pancreas releases insulin to lower blood glucose and glucagon to raise it.
• Adrenal glands produce cortisol (increase blood glucose), aldosterone (increase blood sodium), adrenaline, and noradrenaline (affect heart rate and blood pressure).

Explore the essential functions of the endocrine system, focusing on the pituitary and adrenal glands. This quiz covers hormone secretion, regulation of bodily functions, and the role of mineralocorticoids and glucocorticoids. Test your knowledge on how these hormones affect health and balance.