[THE CLINICAL APPROACH TO DIAGNOSIS AND TREATMENT OF HYPOTHYROIDISM].

Hypothyroidism is the most frequent endocrinologic disorder after diabetes. It is caused by the insufficient production of thyroid hormones Thyroxine (T4) and Triiodothyronine (T3). T4 is the main hormone that is accumulated in the thyroid gland, while T3 is the active hormone that is produced from T4 in the peripheral tissues. More than 99% of the patients have primary hypothyroidism which is due to thyroid disorder mainly Hashimoto's thyroiditis or iatrogenic. Hypothyroidism is divided into sub-clinical when T4 is in the normal range and overt when it is low and usually the TSH level is higher than 10 mIU\L. The diagnosis is based on blood tests, because the signs and symptoms are neither specific nor sensitive. In the elderly, the upper limit of normal TSH level is higher than that reported by the laboratory in Israel and in healthy young it is lower. TSH is the most sensitive tool for screening, diagnosis and treatment follow-up when the pituitary is normal. The drug of choice in hypothyroidism is Levothyroxine (T4 salt) which is very effective, well tolerated and inexpensive.