In autoimmune Hashimoto thyroiditis, what hormone deficiency is primary?

• A. Thyroid hormones (T4 and T3)
• B. TSH
• C. Calcitonin
• D. TRH

Answer: (A)

Hashimoto thyroiditis is an autoimmune attack on the thyroid gland that reduces its ability to produce thyroid hormones. The primary deficiency here is in the thyroid hormones themselves, specifically T4 and T3, because the gland’s tissue is damaged and cannot synthesize adequate amounts. As a result, levels of these hormones fall, and the pituitary responds by increasing TSH in an attempt to stimulate the thyroid. This explains why TSH is typically elevated in this condition rather than deficient. Calcitonin, produced by C cells, is not the hormone affected in Hashimoto. TRH is a hypothalamic hormone that regulates TSH release; a deficiency would point to a hypothalamic issue, not autoimmune destruction of the thyroid. Therefore, the main deficiency in Hashimoto is T4 and T3.