Iatrogenic Hypothyroidism and Its Sequelae

Iatrogenic hypothyroidism can be permanent, when induced by a treatment leading to a permanent thyroid damage, or reversible, when caused by drugs interfering with thyroid function. The incidence of surgical hypothyroidism is mainly influenced by the extent of surgery. Drugs can interfere with TSH secretion, thyroid hormone synthesis and secretion, absorption of levo-thyroxine and the metabolism of thyroid hormone. Clinical expression of hypothyroidism is mainly influenced by its rate of development and patient’s age. In primary hypothyroidism, low concentrations of thyroid hormones associated with high levels of serum TSH identify clinical hypothyroidism, whereas subclinical hypothyroidism is characterized by an isolated rise of TSH levels. Replacement treatment is required in all patients after total thyroidectomy whereas in presence of clinical or subclinical hypothyroidism after partial thyroidectomy the replacement therapy should be initiate at lower doses. Synthetic levo-thyroxine (L-T4) is recommended for the treatment of hypothyroidism. A correct treatment during pregnancy is required to avoid the consequence of fetal hypothyroidism and, in hypothyroid women of childbearing age who are planning pregnancy, L-T4 treatment should be adjusted in order to maintain a TSH value <2.5 mIU/l. Treatment of subclinical hypothyroidism should be supported, or at least not discouraged.