Circulating thyroid antibodies and thyroid function studies in children and adolescents with insulin-dependent diabetes mellitus

Abstract

Significant high titres (1∶400–1∶25,600) of circulating thoroid microsomal antibodies (MCHA) were found in the sera of 5 out of 59 non-ketoacidotic, insulin-dependent diabetic (IDDM) patients (mean age 14.5 years). Among these five patients (four females, one male), all of whom were over 11 years, two also had thyroglobulin antibodies. Increased thyrotropin (TSH) response to TRH was found in 3/5 MCHA positive patients and in 3/54 without circulating MCHA. Serum thyroxine (T₄) and free T₄ (FT₄) average values were significantly lower (P<0.01 and P<0.001) in diabetics (7.1±1.8μg/dl and 10.2±3.1 pg/ml, x±SD) as compared to normal sex and age matched controls (8.9±1.9 μg/dl and 12.2±2.2 pg/ml, respectively). T₄ and FT₄ values were inversely related to the duration of the disease. Subnormal T₄ values were found in six (five females and one male) patients, four of whom had subnormal FT₄ values. No patient had low triiodothyronine (T₃) and high reverse T₃ (rT₃) values, i.e. none displayed the biochemical pattern of the ‘low T₃ syndrome’ described with ketoacidotic status. This indicates also a satisfactory compensation of IDDM in all the patients. At the time of study no patient (including also those with circulating MCHA and TGHA and with TSH hyper-response to TRH) showed either thyroid size enlargement or clinical features of thyroid dysfunction including impaired growth and bone age retardation.