Which of these occurs as a response to a thyroidectomy ?

Options

A. Decreased TRH secretion
B. Increases TRH secretion
C. Increased calcitonin secretion
D. Increased `T_(3)` and `T_(4)` secretion

Answer

**Step-by-Step Solution:**

1. **Understanding Thyroidectomy**: Thyroidectomy is a surgical procedure that involves the removal of the thyroid gland, which is located in the neck. This gland plays a crucial role in hormone production.

2. **Role of the Thyroid Gland**: The thyroid gland produces important hormones, primarily T3 (triiodothyronine) and T4 (thyroxine). These hormones are essential for regulating metabolism, growth, and development.

3. **Hormonal Regulation**: The release of T3 and T4 is regulated by a feedback mechanism involving the hypothalamus and the pituitary gland. The hypothalamus releases Thyroid Releasing Hormone (TRH), which stimulates the anterior pituitary to release Thyroid Stimulating Hormone (TSH). TSH then stimulates the thyroid gland to produce T3 and T4.

4. **Impact of Thyroidectomy**: When the thyroid gland is removed, the production of T3 and T4 ceases. However, the hypothalamus continues to release TRH, and the anterior pituitary continues to release TSH because they are still intact and are not aware that the thyroid gland has been removed.

5. **Compensatory Mechanism**: In response to the absence of T3 and T4, the hypothalamus will increase the secretion of TRH in an attempt to stimulate the pituitary gland to produce more TSH. However, since the thyroid gland is absent, TSH cannot stimulate T3 and T4 production.

6. **Conclusion**: Therefore, the key responses to thyroidectomy include increased TRH secretion, increased TSH secretion, and decreased (or absent) T3 and T4 secretion.

**Final Answer**: After a thyroidectomy, the responses include increased TRH secretion, increased TSH secretion, and decreased T3 and T4 secretion.

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