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 not been studied in different etiologic groups.


METHODS
This study assessed the influence of age on optimal daily LT. dosage in 337 patients with primary hypothyroidism grouped according to etiology.


RESULTS
Daily LT. dosage declined with increasing age in 99 patients with Hashimoto's thyroiditis, in 73 patients with idiopathic variety, and in 47 patients with hypothyroidism due to radical neck surgery and/or neck radiation for non-thyroidal malignancies. In contrast, daily LT. dosage rose with age in 85 patients who had radioiodine (131I) therapy and/or subtotal thyroidectomy for hyperthyroidism. Finally, daily LT. dosage was not significantly altered in 22 patients with subclinical hypothyroidism or in 11 patients with drug-induced hypothyroidism.


CONCLUSIONS
Optimal daily LT4 dosage does not decline universally in all elderly with primary hypothyroidism: it appears to depend also on the etiology of the disorder.
Kabadi
U M
UM
VA Medical Center Des Moines, Iowa, USA.
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging; D000638:Amiodarone / Q000009:adverse effects; D000889:Anti-Arrhythmia Agents / Q000009:adverse effects; D018692:Antimanic Agents / Q000009:adverse effects; D005260:Female; D006801:Humans; D006980:Hyperthyroidism / Q000532:radiotherapy / Q000601:surgery; D007037:Hypothyroidism / Q000139:chemically induced / Q000188:drug therapy* / Q000209:etiology; D007457:Iodine Radioisotopes / Q000627:therapeutic use; D016651:Lithium Carbonate / Q000009:adverse effects; D008297:Male; D008875:Middle Aged; D009333:Neck / Q000528:radiation effects / Q000601:surgery; D019275:Radiopharmaceuticals / Q000627:therapeutic use; D013961:Thyroid Gland / Q000528:radiation effects; D013965:Thyroidectomy; D013966:Thyroiditis / Q000150:complications; D013967:Thyroiditis, Autoimmune / Q000150:complications; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000008:administration & dosage* / Q000097:blood; D014284:Triiodothyronine / Q000097:blood
D000889:Anti-Arrhythmia Agents; D018692:Antimanic Agents; D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals; D014284:Triiodothyronine; D016651:Lithium Carbonate; D013972:Thyrotropin; D000638:Amiodarone; D013974:Thyroxine