Which among the following is an Endocrine gland in the human body?

Correct Answer: C

Rationale: The pituitary gland, an endocrine gland, secretes hormones (e.g., GH, TSH) into the bloodstream, dubbed the 'master gland' for regulating others. Salivary, digestive (e.g., pancreas exocrine), and sweat glands are exocrine, using ducts not blood for secretions. Pituitary's ductless, systemic influence distinguishes it, critical for endocrine coordination, contrasting with exocrine functions.

Correct Answer: B

Rationale: Adrenal medulla, secreting epinephrine/norepinephrine, isn't essential life persists post-adrenalectomy with cortical steroids. Zona fasciculata secretes cortisol, not aldosterone (glomerulosa). ACTH mainly controls cortisol, not glomerulosa's aldosterone (angiotensin II does). Medullary secretion is ~80% epinephrine, not norepinephrine. Non-essentiality distinguishes medulla, key to understanding adrenal roles, unlike zonal, control, or output errors.

Correct Answer: B

Rationale: Free cortisol feeds back negatively on both pituitary (ACTH) and hypothalamus (CRH) false to exclude hypothalamus. Suprachiasmatic nuclei drive ACTH's diurnal rhythm. Haemorrhage boosts aldosterone (RAAS) and cortisol (stress). Testosterone inhibits LH. Hypothalamic feedback distinguishes cortisol's regulation, key to HPA axis, unlike rhythm, stress, or gonadal truths.

Correct Answer: A

Rationale: PTH decreases serum PO₄ by increasing renal excretion, raising Ca²⁺ net effect is PO₄ reduction. Vitamin D increases Ca/PO₄ absorption, reducing excretion opposite claim. Calcitonin is from thyroid C-cells, not parathyroid. Insulin promotes bone formation (anabolic), not decreases. PTH's PO₄-lowering distinguishes it, key to calcium-phosphate regulation, unlike vitamin D, calcitonin, or insulin errors.

Correct Answer: C

Rationale: Oestrogen inhibits osteoclasts, reducing bone resorption, preserving mass post-menopause osteoporosis link. Ca is ~1-2% body mass, not 15%. Intestinal Ca absorption is active (vitamin D), not passive. Corticosteroids inhibit osteoblasts, promoting loss. Oestrogen's osteoclast suppression distinguishes it, key to bone health, unlike mass, absorption, or steroid errors.