Assessing Hypothyroidism in the Preparation of Patients With Thyroid Cancer

Abstract

This study evaluated the effects of iatrogenic hypothyroidism in patients with thyroid carcinoma on cardiovascular risk, renal function, drug metabolism, persistence of elevated thyroid-stimulating hormone (TSH), and absence from work. Serum levels of C-reactive protein, low-density lipoprotein cholesterol, lipoprotein a, apolipoprotein B, and malonyl dialdehyde, as well as microalbuminuria and creatinine clearance, were determined in 31 patients during levothyroxine treatment (TSH ranging from 0.05 to 0.5 mIU/mL) and 5 weeks after thyroxine withdrawal with triiodothyronine given during the first 2 weeks. TSH values >65 mIU/mL were observed in all patients. Two months after reintroduction of levothyroxine, 26% of the patients still showed TSH levels >5 mIU/mL. The mean number of missed days of work resulting from hypothyroidism was 8.7 days. Except for creatinine clearance, which was significantly reduced, all other parameters studied increased during hypothyroidism. We also present 2 cases of marked elevation of serum digoxin and phenobarbital levels during acute hypothyroidism. This study demonstrates that hypothyroidism induced to prepare patients with thyroid carcinoma for therapy is persistent and associated with a significant increase in risk factors for atherosclerosis, decrease in renal function, changes in drug metabolism, and important absence from work. We suggest that recombinant TSH should be the preparation of choice, thus freeing the patients from these and other undesired effects.