INFLUENCE OF AGE ON OPTIMAL DAILY LEVOTHYROXINE DOSAGE IN PATIENTS WITH PRIMARY HYPOTHYROIDISM GROUPED ACCORDING TO ETIOLOGY

Background. Optimal daily levothyroxine (LT4) dosage is reported to be significantly smaller in the elderly with primary hypothyroidism when compared with their younger counterparts. However, this finding has n ot been studied in different etiologic groups. Methods. This study ass essed the influence of age on optimal daily LT4 dosage in 337 patients with primary hypothyroidism grouped according to etiology. Results. D aily LT4 dosage declined with increasing age in 99 patients with Hashi mots's thyroiditis, in 73 patients with idiopathic variety and in 47 p atients with hypothyroidism due to radical neck surgery and/or neck ra diation for non-thyroidal malignancies. in contrast, daily LT4 dosage rose with age in 85 patients who had radioiodine (I-131) therapy and/o r subtotal thyroidectomy for hyperthyroidism. Finally, daily LT4 dosag e was not significantly altered in 22 patients with subclinical hypoth yroidism or in 11 patients with drug-induced hypothyroidism. Conclusio n. Optimal daily LT4 dosage does not decline universally in all elderl y with primary hypothyroidism; it appears to depend also on the etiolo gy of the disorder.