Final answer:
The hypothalamus secretes regulatory hormones through the hypophyseal portal system to control the secretion of the anterior pituitary gland's hormones, including TSH and GH. Elevated thyroid hormones T3 and T4 feedback to inhibit further secretion. GHRH from the hypothalamus stimulates growth hormone release from the anterior pituitary.
Step-by-step explanation:
The hypothalamic-pituitary-thyroid axis is a critical endocrine system that regulates metabolism, growth, and development. The hypothalamus plays a pivotal role by secreting regulatory hormones into the hypophyseal portal system, directly affecting the anterior pituitary gland. The anterior pituitary produces several hormones, including thyroid-stimulating hormone (TSH), which stimulates the thyroid gland to release thyroid hormones T3 and T4.
When thyroid hormones levels rise, they signal both the hypothalamus and anterior pituitary to reduce the release of regulatory hormones and TSH, creating a negative feedback loop. Specific to growth hormone (GH), the hypothalamus releases growth hormone-releasing hormone (GHRH), which reaches the anterior pituitary and stimulates GH secretion.