The antagonistic hormone to calcitonin is

Correct Answer: D

Rationale: PTH (parathyroid) raises blood calcium by bone resorption, opposing calcitonin's lowering via deposition antagonistic pair. Thyroxine (thyroid) boosts metabolism, not calcium directly. GH (pituitary) grows bones, not regulating calcium. Insulin (pancreas) lowers glucose, unrelated. PTH's calcium-raising role distinguishes it, key to homeostasis, unlike metabolic, growth, or glucose hormones.

Correct Answer: D

Rationale: Type I diabetes (IDDM) requires insulin injections autoimmune β-cell loss halts production. Obesity correlates with type II, not I. Type II is more common insulin resistance. Resistance defines type II, not I cells respond, lack insulin. Injection need distinguishes type I, key to its management, unlike obesity, prevalence, or resistance traits.

Correct Answer: C

Rationale: ANH, aldosterone, and ADH regulate blood pressure/volume ANH lowers (natriuresis), aldosterone/ADH raise (sodium/water retention). Oxytocin (hypothalamus) drives labor/milk ejection, not pressure/volume reproductive focus. Oxytocin's exclusion distinguishes it, key to its non-vascular role, unlike volume-regulating trio.

Correct Answer: A

Rationale: Insulin (pancreas) drives glucose uptake into cells (e.g., muscle) via GLUT4 lowers blood sugar. Renin (kidneys) initiates RAAS, not glucose-focused. Angiotensin (blood) raises pressure, unrelated. Melatonin (pineal) regulates sleep, not metabolism. Insulin's glucose transport role distinguishes it, critical for energy homeostasis, unlike pressure or sleep hormones.

Correct Answer: C

Rationale: Epinephrine and norepinephrine from the adrenal medulla trigger the fight-or-flight response rapid heart rate, glucose mobilization not thyroxine/melatonin (metabolism/sleep), insulin/glucagon (glucose regulation), or oestrogen/progesterone (reproduction). This distinguishes catecholamines' acute stress role, key to survival, a classic NEET endocrine distinction.