THYROID STATUS OF PATIENTS RECEIVING LONG-TERM ANTICONVULSANT THERAPYASSESSED BY PERIPHERAL PARAMETERS - A PLACEBO-CONTROLLED THYROXINE THERAPY TRIAL

Thyroid hormone concentrations and measures reflecting thyroid functio n were studied in sera from 35 patients receiving long-term phenytoin (PHT) or carbamazepine (CBZ) therapy, The mean concentrations of T-4, FT4, FT3, and rT(3), but not T-3, of these patients were significantly lower than those of 19 controls of similar age and sex distribution, The mean serum thyrotropin (TSH) concentration was slightly but signif icantly higher in patients than in controls, but the serum TSH respons e to TRH was not significantly increased. In patients, the higher mean clinical diagnostic index of hypothyroidism (CDI-HT: -20.3 +/- 19.1 v s. -33.7 +/- 8.5, p < 0.05) and higher ratio of preejection period to left ventricular ejection time (PEP/LVET: 0.343 +/- 0.065 vs, 0.334 +/ - 0.030, p < 0.05) than in controls were compatible with tissue hypoth yroidism, However, comparison of the mean levels of alanine aminotrans ferase (ALAT), creatine kinase (CK), creatinine, triglycerides, choles terol, high-density lipoprotein (HDL) cholesterol, osteocalcin, procol lagen type III aminoterminal propeptide, and somatomedin-C showed no s ignificant differences between patients and controls. The increased me an angiotensin convertase and sex hormone-binding globulin (SHBG) leve ls, typical of hyperthyroidism, were probably caused by drug effects, Fourteen patients with a subnormal FT4 concentration in serum particip ated in a double-blind thyroxine treatment cross-over study, Neither t he mean CDI-HT score, nor the systolic time intervals were significant ly different be tween the thyroxine and placebo periods. Five patients benefited subjectively from the treatment, On the basis of all data f rom the cross-sectional and thyroxine treatment studies, we conclude t hat patients receiving anticonvulsant drugs chronically are eumetaboli c and do not need thyroxine supplementation.