Levothyroxine is a replacement therapy for which hormone?

Levothyroxine is a replacement therapy for which hormone?

• A. T3
• B. T4
• C. Calcitonin
• D. PTH

Answer: (B)

Levothyroxine replaces thyroxine (T4), the hormone the thyroid gland normally produces. In hypothyroidism, the goal is to restore the missing thyroid hormone to normalize metabolic processes. The body then converts T4 to T3, the active form, in tissues as needed. A synthetic, long-acting T4 preparation provides steady hormone levels and easier dosing, which is why it’s the standard replacement therapy for thyroid hormone deficiency. The other hormones mentioned—calcitonin and parathyroid hormone—are unrelated to this thyroid hormone replacement. T3 can be used in some cases, but it fluctuates more and isn’t the first-line option for routine replacement.

Levothyroxine replaces thyroxine (T4), the hormone the thyroid gland normally produces. In hypothyroidism, the goal is to restore the missing thyroid hormone to normalize metabolic processes. The body then converts T4 to T3, the active form, in tissues as needed. A synthetic, long-acting T4 preparation provides steady hormone levels and easier dosing, which is why it’s the standard replacement therapy for thyroid hormone deficiency. The other hormones mentioned—calcitonin and parathyroid hormone—are unrelated to this thyroid hormone replacement. T3 can be used in some cases, but it fluctuates more and isn’t the first-line option for routine replacement.