Which of the following is an endocrine-exocrine gland?

Correct Answer: D

Rationale: The pancreas is both endocrine (islets secrete insulin/glucagon into blood) and exocrine (acinar cells release digestive enzymes via ducts). Adrenal, pituitary, and thyroid are purely endocrine, secreting hormones (e.g., cortisol, GH, thyroxine) into blood, no ducts. Pancreas' dual role regulating glucose and aiding digestion distinguishes it, vital for metabolic and digestive integration, unlike single-function glands.

Correct Answer: B

Rationale: Paracrine signaling involves chemicals, like prostaglandins, affecting nearby cells, as in inflammation. Autocrine signals target the secreting cell itself (e.g., cancer cells), endocrine signals travel via blood to distant targets, and 'neuron' isn't a signaling type neurons use neurotransmitters. Paracrine's local action distinguishes it, key for short-range cellular communication, contrasting with self-directed or systemic signaling in physiological responses.

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: B

Rationale: Pinealocytes in the pineal gland secrete melatonin to regulate sleep-wake cycles, influenced by light. Melanocytes produce pigment, suprachiasmatic nucleus cells regulate circadian rhythms but don't secrete melatonin, and retinal cells detect light. Pinealocytes' secretory role distinguishes them, vital for circadian control, contrasting with pigment or regulatory cells.

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.