Human Endocrine System

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.

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'.

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.

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.

Growth hormone (somatotropin) primarily stimulates the growth of muscle, cartilage, bone and connective tissues. It promotes protein synthesis and cell division in these tissues, making it essential for physical growth.

Thyroxine (T4) is the main hormone secreted by the thyroid gland and controls tissue metabolism by regulating basal metabolic rate. It influences oxygen consumption, heat production, and metabolic activity in cells.

The thyroid gland secretes thyroxine continuously, not in bursts or periodically. This continuous secretion maintains steady metabolic control. Seasonal secretion or puberty-only secretion would cause metabolic fluctuations.

Oxytocin is a small peptide hormone composed of 9 amino acids. It is not a large peptide, fatty acid, or sugar molecule. Peptide hormones are classified by their amino acid chain length.

Growth hormone (somatotropin) is directly secreted by the pituitary gland. Release factors and inhibiting factors come from the hypothalamus, not the pituitary. The pituitary secretes the hormones themselves, not the release factors.

Adrenaline (epinephrine) is produced by the adrenal medulla. Corticosterone, aldosterone, and cortisol are produced by the adrenal cortex, not the medulla. The medulla specializes in catecholamine production.

Glucocorticoids (such as cortisol) are catabolic hormones that stimulate proteolysis - the breakdown of proteins into amino acids, particularly during fasting, stress, or hibernation. These amino acids can then be used for gluconeogenesis to maintain blood glucose levels. Secretin stimulates digestive secretions, adrenalin (epinephrine) is primarily involved in acute stress response, and enterogastrone inhibits gastric secretions.

Prolactin is a peptide hormone produced by the anterior pituitary gland that stimulates milk production. Testosterone, oestradiol-17B, and progesterone are all steroid hormones derived from cholesterol, characterized by their four-ring structure. Steroid hormones include sex hormones (androgens, estrogens, progestins) and corticosteroids.

Oestrogens, androgens, progestins, and corticosteroids are all classes of steroid hormones. They share a common chemical structure based on four fused rings and are synthesized from cholesterol. Prostaglandins are lipid-derived eicosanoids, juvenile hormones are insect growth regulators, and these options don't fit the classification.

Glucagon is the primary hormone that increases blood glucose levels during fasting, exercise, or stress. It stimulates glycogenolysis (breakdown of glycogen to glucose) in the liver and gluconeogenesis (formation of glucose from non-carbohydrate sources). Insulin lowers blood glucose by promoting glucose uptake, somatostatin inhibits both glucagon and insulin secretion, so 'all of the above' is incorrect.