Hypothyroidism	

Iodine deficiency is the most common cause of goitre and borderline hypothyroidism world-wide. In non iodine-deficient areas, however, autoimmunity is the most common cause of hypothyroidism (Fig. 15.19). Destructive therapy by surgery or radioiodine for thyrotoxicosis accounts for approximately one-third of all cases. Excessive iodine (e.g. as a result of chronic ingestion of proprietary cough medicines) may also cause hypothyroidism. Primary hypothyroidism due to failure of the thyroid gland itself is much more common than failure secondary to pituitary dysfunction, or tertiary hypothyroidism due to hypothalamic disease.