ADH is secreted by?
**Core Concept**
The **hypothalamic-pituitary axis** plays a crucial role in regulating various bodily functions, including water balance. **Antidiuretic hormone (ADH)**, also known as vasopressin, is a key hormone involved in this process. It is produced in the **hypothalamus** and released by the **posterior pituitary gland**.
**Why the Correct Answer is Right**
ADH is synthesized in the **supraoptic** and **paraventricular nuclei** of the **hypothalamus**. From there, it travels down the **axons** of these neurons to the **posterior pituitary gland**, where it is stored and released into the bloodstream. This hormone helps regulate water balance by increasing **water reabsorption** in the **collecting ducts** of the **kidneys**.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because ADH is not primarily secreted by this gland.
**Option B:** Incorrect as it is not the primary site of ADH secretion.
**Option C:** Incorrect because, although the hypothalamus is the site of ADH production, it is not the site of its secretion.
**Clinical Pearl / High-Yield Fact**
Remember that **central diabetes insipidus** is a condition characterized by the inability to secrete ADH, leading to **polyuria** and **polydipsia**.
**Correct Answer:** D. Posterior pituitary gland.