**Core Concept**
Glucocorticoids, a class of corticosteroids, exert their effects through negative feedback mechanisms on the hypothalamic-pituitary-adrenal (HPA) axis. They play a crucial role in regulating the body's response to stress and inflammation.

**Why the Correct Answer is Right**
Glucocorticoids suppress the release of Adrenocorticotropic Hormone (ACTH) from the anterior pituitary gland. ACTH stimulates the secretion of cortisol from the adrenal cortex. By inhibiting ACTH release, glucocorticoids create a negative feedback loop that maintains homeostasis in the HPA axis. This mechanism is essential for preventing excessive cortisol production and associated side effects.

**Why Each Wrong Option is Incorrect**
**Option A:** Growth Hormone (GH) is not directly suppressed by glucocorticoids. GH is primarily regulated by the hypothalamus through the release of Growth Hormone-Releasing Hormone (GHRH) and Somatostatin.
**Option C:** Follicle-Stimulating Hormone (FSH) is a gonadotropin involved in reproductive function, which is not directly affected by glucocorticoids. FSH is regulated by Gonadotropin-Releasing Hormone (GnRH) from the hypothalamus.
**Option D:** Luteinizing Hormone (LH) is another gonadotropin involved in reproductive function, which is not directly suppressed by glucocorticoids. LH is also regulated by GnRH from the hypothalamus.

**Clinical Pearl / High-Yield Fact**
Glucocorticoids can cause adrenal insufficiency when used chronically, which is a potential pitfall in patients on long-term steroid therapy. This is because glucocorticoids suppress ACTH release, leading to decreased cortisol production from the adrenal cortex.

**✓ Correct Answer: B. ACTH. ACTH.**