The secretion of thyroid hormones is controlled by

Correct Answer: B

Rationale: Thyroid-stimulating hormone (TSH) from the anterior pituitary stimulates thyroid hormone (T3/T4) release, regulated by hypothalamic TRH. TSH isn't hypothalamic, thyroxine isn't pituitary-made, and thyroglobulin is a thyroid storage protein, not a controller. TSH's pituitary origin distinguishes it, central to the hypothalamic-pituitary-thyroid axis, critical for metabolic regulation.

Correct Answer: C

Rationale: Erythropoietin (EPO), from kidneys, stimulates red blood cell production, increasing oxygen-carrying capacity enhancing endurance. It doesn't affect calcium, growth hormone, or muscle mass directly (testosterone does). Oxygen boost distinguishes EPO's use, key to athletic performance, contrasting with skeletal or hormonal growth effects.

Correct Answer: C

Rationale: Gonads (ovaries, testes) produce steroid hormones testosterone, estrogen, progesterone from cholesterol, acting on nuclear receptors for sex traits and reproduction. Amine hormones (e.g., thyroxine) derive from tyrosine/tryptophan, from thyroid. Peptide hormones (e.g., insulin) are protein-based, from pancreas. Catecholamines (e.g., epinephrine) are adrenal medullary, not gonadal. Steroids' lipid-soluble, genomic action distinguishes them, critical for gonadal endocrine function, unlike amino-acid or peptide classes.

Correct Answer: C

Rationale: Melatonin, from the pineal gland, regulates sleep-wake cycles, peaking in darkness to induce sleep, reducing arousal and cortisol darkness triggers, light inhibits it. The false statement reverses this: light suppresses melatonin, resetting circadian rhythms, while darkness stimulates it. Heat loss and rhythm regulation are true effects; pineal production is accurate. This light-dark dynamic distinguishes melatonin's role, critical for circadian alignment, unlike inverted or correct functions.

Correct Answer: C

Rationale: Addison's disease, adrenocortical insufficiency, causes glucocorticoid/mineralocorticoid deficiency, leading to muscle weakness, tiredness, hypoglycemia (not hyperglycemia), and menstrual issues from cortisol lack. Hyperglycemia aligns with excess cortisol (Cushing's). Hypoglycemia distinguishes Addison's metabolic impact, critical for recognizing adrenal failure, contrasting with sugar-elevating conditions.