Human Endocrine System

Addison's disease occurs when the adrenal cortex is destroyed or dysfunctional, leading to deficient secretion of glucocorticoids and mineralocorticoids. This causes fatigue, low blood pressure, and electrolyte imbalances. Option A correctly identifies the adrenal hyposecretion as the root cause.

Androgens are steroid hormones that regulate male characteristics and reproduction, including testosterone. They are produced primarily in the gonads (testes in males, ovaries in females) and adrenal glands. Option A correctly identifies androgen as a hormone class.

Simmond's disease (panhypopituitarism) results from pituitary destruction, causing deficiency of all pituitary hormones. This leads to myxoedema - thickened, dry skin from thyroid hormone deficiency, among other symptoms. Option D correctly identifies this association.

Enterogastrone is a hormone secreted by the intestinal mucosa when acidic chyme enters the small intestine. It inhibits gastric acid secretion and stomach motility, protecting the duodenum and slowing gastric emptying. Option C correctly describes this inhibitory function.

Parathormone (PTH) from the parathyroid glands increases blood calcium by stimulating bone resorption, kidney calcium reabsorption, and vitamin D activation. This directly opposes calcitonin. Option B correctly identifies PTH as the calcium-raising hormone.

Ecdysone is the molting hormone in insects and other arthropods, produced by prothoracic glands. It triggers metamorphosis and molting by regulating gene expression. Option C correctly identifies insects as the source.

Hypophysectomy is the surgical removal of the pituitary gland (hypophysis), used historically to treat cancers and study endocrine function. The prefix 'hypo-' refers to the pituitary, and '-ectomy' means removal. Option A correctly identifies this term.

Diabetes mellitus results from insufficient insulin production or action. The pancreas contains beta cells that secrete insulin; when these fail, blood glucose regulation is impaired. Options A, B, and C are not primarily responsible. Option D correctly identifies the pancreas.

The pancreas is an endocrine gland secreting insulin (from beta cells) and glucagon (from alpha cells). These are opposing hormones regulating blood glucose - insulin lowers it, glucagon raises it. Options B and C list pituitary/gonadal hormones. Option A is correct.

The adrenal medulla secretes epinephrine and norepinephrine during stress, initiating the 'fight-or-flight' response - increased heart rate, blood pressure, and energy mobilization. This rapid response to emergencies earns the title 'emergency gland'. Option C is correct.

Epinephrine (adrenaline) is a catecholamine hormone produced by the adrenal medulla. It is not a kidney structure (glomeruli), embryonic tissue (mesoderm), or nephridial part. Options A, B, and D describe anatomical structures incorrectly. Option C correctly identifies epinephrine as an adrenal hormone.

Insulin and glucagon are protein hormones composed of amino acid chains, making them polypeptides. Insulin has two polypeptide chains; glucagon is a single chain. They are not carbohydrates (polysaccharides) or nucleic acids (polynucleotides). Option A correctly classifies them.

Adrenaline (epinephrine) binds to beta-1 adrenergic receptors in the heart, increasing heart rate, force of contraction, and cardiac output. This is part of the sympathetic 'fight or flight' response. Gastrin stimulates gastric acid secretion, glucagon raises blood glucose, and thyroxine regulates basal metabolism but does not directly stimulate cardiac function like adrenaline does.

Glucocorticoids like cortisol stimulate gluconeogenesis (formation of glucose from non-carbohydrate sources) in the liver, which enhances overall glucose formation. They also promote protein catabolism to provide amino acid substrates for this process. Options C and D describe mineralocorticoid (aldosterone) effects on sodium balance, not glucocorticoid effects.

Insulin has multiple metabolic effects: it lowers blood glucose by promoting glycogenesis (glucose storage as glycogen) in liver and muscle; inhibits gluconeogenesis in the liver; promotes cellular uptake of amino acids; and prevents breakdown of fat and protein in adipose tissue and muscles. Since options A, B, and C are all valid insulin actions, 'all of the above' is correct.

Cushing's syndrome results from excessive cortisol production (hypercortisolism) from the adrenal cortex. This can be due to adrenal tumors, pituitary ACTH-secreting tumors, or exogenous corticosteroid administration. Symptoms include weight gain, moon face, buffalo hump, and hyperglycemia. Decreased cortisol would cause Addison's disease, not Cushing's.

Somatotropic hormone (growth hormone, GH) is synthesized and secreted by somatotroph cells in the anterior pituitary gland. It stimulates growth, cell reproduction, and regeneration. The pancreas secretes insulin and glucagon, the adrenal secretes catecholamines and corticosteroids, and the thyroid secretes thyroid hormones - none of which are somatotropic hormone.

Gluconeogenesis is the metabolic pathway of producing glucose from non-carbohydrate substrates like amino acids (from protein breakdown), lactate (from anaerobic glycolysis), and glycerol (from fat breakdown). Glycogenolysis is glycogen breakdown, glycogenesis is glycogen synthesis, so the correct answer is gluconeogenesis.

Calcitonin LOWERS plasma calcium levels by inhibiting bone resorption (osteoclast activity) and increasing calcium excretion by kidneys. It also lowers plasma phosphate. The question asks for the 'odd one out' - option A claims calcitonin raises calcium, which is incorrect and therefore the exception. However, the phrasing is confusing since calcitonin doesn't do any of these directly - it inhibits bone resorption which indirectly lowers calcium.

Secretin is the primary hormone that stimulates the pancreas to secrete pancreatic juice (rich in bicarbonate to neutralize acidic chyme). It is released from S cells in the duodenum when acidic chyme enters the small intestine. Trypsinogen is a pancreatic enzyme precursor, enterokinase activates trypsinogen, and cholecystokinin stimulates enzyme secretion but fluid/bicarbonate secretion is mainly secretin-driven.

Estradiol (estrogen) and progesterone are the primary female sex hormones produced by ovaries. They regulate the menstrual cycle, pregnancy, and secondary sexual characteristics. Adrenocorticotropic is a pituitary hormone, androgens are male hormones, testosterone is the primary male sex hormone - none of which constitute the 'set of female hormones'.

The corpus luteum secretes progesterone, which maintains the endometrial lining for potential embryo implantation and supports early pregnancy until the placenta takes over. This function is essential for 'retention of pregnancy'. Childbirth is triggered by oxytocin, ovulation is caused by LH surge, and milk production is stimulated by prolactin - not corpus luteum functions.

Oxytocin and Antidiuretic Hormone (ADH, vasopressin) are synthesized in the hypothalamus and stored/released from the POSTERIOR pituitary. The question uses the imprecise term 'secreted in' but the intended answer is posterior pituitary hormones. Glucagon is from pancreas, insulin is from pancreas - so the pair in the posterior pituitary is oxytocin and ADH.

Gamma-aminobutyric acid (GABA) is the primary inhibitory neurotransmitter in the central nervous system. It binds to GABA receptors (GABA-A and GABA-B) causing hyperpolarization of neurons by opening chloride channels, reducing neuronal excitability. Adrenaline is excitatory, acetylcholine can be excitatory at neuromuscular junctions, and histamine has various effects including excitatory roles in arousal and wakefulness.

Oxytocin, the hormone responsible for uterine contractions during childbirth and milk ejection during breastfeeding, is synthesized in the hypothalamus and stored and released by the posterior pituitary gland. The anterior pituitary produces different hormones like growth hormone and prolactin.