Comprehensive Diabetes and Thyroid Disorders: Pathophysiology, Symptoms, and Management Practice Test

Thyroid hormone production requires iodine. When dietary iodine is insufficient, the thyroid can’t synthesize enough T3 and T4, lowering the metabolic rate. In response, the pituitary increases TSH to stimulate the thyroid, often causing enlargement of the gland (goiter) and the signs of hypothyroidism. Among the options, iodine deficiency is the direct dietary cause of hypothyroidism because iodine is a vital building block for thyroid hormones. Iron deficiency affects other enzymes and oxygen transport but does not directly halt thyroid hormone synthesis the way iodine deficiency does, and vitamin C and calcium deficiencies do not play a direct role in making thyroid hormones.