Hypothyroidism in adults due to an underactive thyroid is

Correct Answer: C

Rationale: Adult hypothyroidism (low T3/T4) causes myxedema fatigue, weight gain, cold intolerance from slow metabolism. Graves is hyperthyroidism opposite. Diabetes insipidus is ADH lack water loss. Acromegaly is GH excess bone growth. Myxedema's hypometabolic state distinguishes it, key to thyroid deficiency, unlike hyperactive, water, or growth conditions.

Correct Answer: C

Rationale: Glucagon (pancreas) opposes insulin by raising blood glucose via glycogenolysis/gluconeogenesis direct antagonist. Cortisol (adrenal) raises glucose longer-term, indirect. Norepinephrine/epinephrine (medulla) spike glucose acutely, stress-related. Mineralocorticoids (aldosterone) manage sodium, not glucose. Glucagon's glucose-elevating role distinguishes it, critical for balance, unlike stress or electrolyte hormones.

Correct Answer: A

Rationale: Melatonin (pineal) regulates sleep-wake cycles, peaking in darkness circadian driver. Water balance is ADH (pituitary), not melatonin. Sexual development ties to gonadal hormones (e.g., testosterone), not pineal puberty onset theories are minor. Sleep regulation distinguishes melatonin, critical for rhythm, unlike water or sex roles.

Correct Answer: C

Rationale: The thyroid, in front of the trachea, secretes T3/T4, setting basal metabolic rate (energy use) and aiding growth (via protein synthesis) neck-based. Brain hosts pituitary/hypothalamus (regulators), not direct producer. Bones lack glands growth target. Adrenals (kidneys) produce cortisol, not metabolism/growth primary. Thyroid's tracheal location distinguishes it, critical for metabolic and developmental regulation, unlike brain, bone, or adrenal sites.

Correct Answer: D

Rationale: Parathormone (PTH) from the parathyroid glands raises blood calcium by enhancing bone resorption, kidney reabsorption, and gut absorption via calcitriol not sodium, which aldosterone manages, nor does it lower calcium (calcitonin's role). This calcium-elevating action distinguishes PTH's homeostatic function, essential for nerve and muscle activity. Confusing sodium or calcium reduction with PTH misaligns its purpose, a common NEET trap highlighting endocrine specificity.