Level of which hormone is likely to increase after hypothalamic ablation?
**Core Concept:** The hypothalamus is a crucial region in the brain responsible for regulating various physiological processes, including the secretion of pituitary hormones. Hypothalamic neurons produce and release hypothalamic releasing or inhibiting factors, which in turn influence the secretion of pituitary hormones.
**Why the Correct Answer is Right:** Hypothalamic ablation would result in the disruption of the normal hypothalamic-pituitary-target organ interactions, leading to an imbalance in hormone secretion. In this case, the correct answer is **D** - thyroid-stimulating hormone (TSH), because the hypothalamus releases thyrotropin-releasing hormone (TRH), which stimulates the anterior pituitary to secrete TSH. TSH in turn stimulates the thyroid gland to produce and release thyroid hormones (thyroxine or T4 and triiodothyronine or T3), which are essential for normal cellular function, growth, and development.
**Why Each Wrong Option is Incorrect:**
A. **Adrenocorticotropic hormone (ACTH):** ACTH is regulated by hypothalamic corticotropin-releasing hormone (CRH), not TRH. Hypothalamic ablation would not directly impact ACTH secretion.
B. **Growth hormone (GH):** GH is regulated by hypothalamic releasing hormone (GHRH) and somatostatin, not TRH. Hypothalamic ablation would not directly impact GH secretion.
C. **Luteinizing hormone (LH) and follicle-stimulating hormone (FSH):** These hormones are regulated by hypothalamic gonadotropin-releasing hormone (GnRH) and inhibiting factor, not TRH. Hypothalamic ablation would not directly impact LH and FSH secretion.
**Clinical Pearl:** Hypothalamic ablation or damage can lead to various endocrine disorders depending on the hypothalamic region involved. In this case, the correct answer is TSH because TRH is released by the paraventricular nucleus and regulates TSH secretion.
**Correct Answer:** D. Thyroid-stimulating hormone (TSH)