Human Endocrine System

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.

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.

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.

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.

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.