Final answer:
The pituitary gland, more specifically the anterior pituitary, regulates the production of thyroid hormone by secreting thyroid-stimulating hormone (TSH).
Step-by-step explanation:
Regulation of Thyroid Hormone Production
The gland that regulates the production of thyroid hormone is the pituitary gland. Specifically, the anterior pituitary secretes thyroid-stimulating hormone (TSH), which stimulates the thyroid gland to produce thyroid hormones, primarily thyroxine (T4) and triiodothyronine (T3). The anterior pituitary itself is regulated by the thyrotropin-releasing hormone (TRH) from the hypothalamus, forming a negative feedback loop with the thyroid gland to maintain hormone levels within a proper range.
Thus, the correct answer to the question "What gland regulates the production of thyroid hormone?" is b. Pituitary.