Question

ADH functions as –

(A). Endocrine
(B). Paracrine
(C). Neurocrine
(D). Autocrine

Choose the correct answer from the options given below:

• A. (A), and (C) only.
• B. (A), (B) and (D) only.
• C. (A), (B), (C) and (D).
• D. (B), (C) and (D) only.

Hint:

ADH is a classic neurohormone.
The term "neurohormone" directly combines neurocrine synthesis (by hypothalamic neurons) and endocrine transport (circulating in the bloodstream to act on the kidneys).

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Chemical messengers can act via different signaling modes depending on the secretory cell type and the pathway taken to reach target cell receptors.

Step 2: Detailed Explanation:
Antidiuretic Hormone (ADH Vasopressin) exhibits two primary functional modes:
1. Neurocrine signaling (C): ADH is synthesized by neurons in the hypothalamus and transported down axons to the posterior pituitary, where it is released from nerve terminals directly into capillary beds. This represents a neurocrine pathway.
2. Endocrine signaling (A): Once released into the blood, ADH travels through systemic circulation to bind to receptors on distant renal collecting duct cells, regulating water permeability. This represents an endocrine pathway.
Therefore, ADH functions as both an endocrine and neurocrine messenger.

Step 3: Final Answer:
The correct option is 1, which corresponds to (A), and (C) only.