Management of hypothyroidism in adults

What are the causes of hypothyroidism?Box 1 lists the important causes of hypothyroidism. The commonest cause of hypothyroidism in developed countries is autoimmune thyroiditis, which may be associated with a goitre (Hashimoto’s thyroiditis) or, with equal frequency, thyroid atrophy. Radioiodine ablation or surgical thyroidectomy as treatment for hyperthyroidism or thyroid cancer are also responsible for important numbers of patients with hypothyroidism. Less often, hypothyroidism may be drug induced (suggesting the possibility of reversibility) or be secondary to disorders of the pituitary or hypothalamus (central or secondary hypothyroidism). Congenital hypothyroidism, due either to thyroid aplasia or hypoplasia or to defective biosynthesis of thyroid hormones, occurs in one per 4000 live births.6 In some parts of the world iodine deficiency remains highly prevalent, with consequent developmental deficits and hypothyroidism affecting infants and children.Box 1 Important causes of hypothyroidism Autoimmune thyroiditis—Hashimoto’s thyroiditis, atrophic autoimmune thyroiditis Iatrogenic—thyroidectomy, radioiodine therapy Thyroiditis—subacute thyroiditis (also known as De Quervain’s thyroiditis), silent thyroiditis, postpartum thyroiditis Iodine deficiency Drugs—carbimazole, methimazole, propylthiouracil, iodine, amiodarone, lithium, interferons, thalidomide, sunitinib, rifampicin Congenital hypothyroidism—thyroid aplasia or hypoplasia, defective biosynthesis of thyroid hormones Disorders of the pituitary or hypothalamus (secondary hypothyroidism)