The body is able to maintain a relatively constant level of thyroid hormone in the blood because a. thyroid hormone stimulates the pituitary to secrete thyroid-stimulating hormone (TSH). b. thyroid hormone inhibits the secretion of TSH-releasing hormone (TRH) from the hypothalamus. c. TRH inhibits the secretion of thyroid hormone by the thyroid gland. d. thyroid hormone stimulates the hypothalamus to secrete TRH.

Verified step by step guidance

1. Identify the role of thyroid hormone in the regulation of its own levels through feedback mechanisms.
2. Understand the relationship between the thyroid gland, pituitary gland, and hypothalamus in the regulation of thyroid hormone.
3. Analyze each statement to determine if it correctly describes a feedback mechanism that would help maintain a constant level of thyroid hormone.
4. Consider how the secretion of TSH and TRH is influenced by the levels of thyroid hormone in the blood.
5. Determine which statement correctly reflects the negative feedback loop necessary for maintaining hormonal balance.

Key Concepts

Thyroid Hormone Regulation

Thyroid hormones, primarily thyroxine (T4) and triiodothyronine (T3), play a crucial role in regulating metabolism and energy levels in the body. Their levels are maintained through a feedback loop involving the hypothalamus and pituitary gland, ensuring that hormone production is adjusted based on the body's needs.

Hypothalamic-Pituitary Axis

The hypothalamic-pituitary axis is a critical regulatory system in the endocrine system. The hypothalamus releases TRH (thyrotropin-releasing hormone), which stimulates the pituitary gland to secrete TSH (thyroid-stimulating hormone), prompting the thyroid gland to produce thyroid hormones. This axis is essential for maintaining hormonal balance.

Negative Feedback Mechanism

Negative feedback is a fundamental biological process where an increase in a substance leads to a decrease in its production. In the context of thyroid hormone regulation, elevated levels of thyroid hormones inhibit the release of TRH and TSH, thereby reducing further hormone production and maintaining homeostasis.