Which structure(s) is/are neuroendocrine in nature?

Correct Answer: D

Rationale: The hypothalamus and posterior pituitary integrate neural and endocrine functions.

Correct Answer: A

Rationale: Elevated GH triggers liver somatomedin (IGF-1) release.

Correct Answer: C

Rationale: Thyroid hormone acts via intracellular nuclear receptors, not G-protein receptors.

Correct Answer: D

Rationale: Somatostatin is secreted by D (delta) cells in the pancreatic islets to regulate insulin and glucagon secretion.

Correct Answer: C

Rationale: Insulin and somatostatin both inhibit glucagon release from A cells. Insulin has disulfide bonds, somatostatin does not; only insulin causes K^+ uptake.