**Question:** Cutting of the pituitary stalk decreases all of the following hormones except -

A. Thyroid-stimulating hormone (TSH)
B. Growth hormone (GH)
C. Prolactin
D. Adrenocorticotropic hormone (ACTH)

**Core Concept:**
The pituitary stalk is a thin, neurovascular bundle that connects the pituitary gland to the hypothalamus. It plays a crucial role in the transport of hormones between the hypothalamus and the pituitary gland. Cutting the pituitary stalk would disrupt this communication, leading to a decrease in hormones that are regulated by the hypothalamus.

**Why the Correct Answer is Right:**
When the pituitary stalk is severed, the following hormones are decreased:
1. Thyroid-stimulating hormone (TSH): TSH is regulated by the hypothalamus, so its production will be affected by the disruption of the hypothalamic-pituitary connection.
2. Growth hormone (GH): GH is also regulated by the hypothalamus, so its production will be impacted by the stalk disruption.
3. Adrenocorticotropic hormone (ACTH): ACTH is regulated by the hypothalamus, and its production will be affected by the stalk severance.

However, **Progesterone** is not regulated by the hypothalamus, and its production is primarily controlled by the corpus luteum in the ovaries during pregnancy. Since progesterone is not part of the hypothalamic-pituitary axis, cutting the stalk would not affect progesterone production.

**Why Each Wrong Option is Incorrect:**

1. Thyroid-stimulating hormone (TSH): TSH is regulated by the hypothalamus via thyrotropin-releasing hormone (TRH), which binds to TSH receptors on the thyroid gland. Disruption of the stalk would lead to decreased TSH, which in turn affects thyroid hormone production.
2. Growth hormone (GH): GH is regulated by the hypothalamus via growth hormone-releasing hormone (GHRH). Similar to TSH, disruption of the stalk would lead to decreased GH production.
3. Adrenocorticotropic hormone (ACTH): ACTH is regulated by the hypothalamus via corticotropin-releasing hormone (CRH). Disruption of the stalk would result in reduced ACTH production, affecting cortisol and aldosterone levels.
4. Progesterone: As explained above, progesterone is primarily regulated by the corpus luteum during pregnancy. Cutting the stalk would not impact progesterone production.

**Clinical Pearls:**

1. The hypothalamic-pituitary-adrenal axis is a critical part of the body's stress response system. Disruption of the hypothalamic-pituitary-adrenal axis due to stalk severance would lead to adrenal insufficiency, which is a life-threatening condition.
2. The hypothalamic-pituitary-ovarian