Relationship of thyroid status and serum N-acetyl- β-glucosaminidase isoenzyme activities in humans

Abstract

Serum from 28 hyperthyroid, hypothyroid, and euthyroid pre- or early puberty females was examined for N-acetyl- β-glucosaminidase (HEX) activity. Total, isoenzyme A (labile), and isoenzyme B (stable) levels were determined for this enzyme. A high degree of correlation ( r = 0.76; p < 0.001) exists between total hexosaminidase activity and thyroid hormone levels (as reflected by the Free Thyroxine Index). Examining each isoenzyme individually, A is selectively enhanced ( r = 0.84; p < 0.0005) whereas B displays no significant change regardless of thyroid activity. In hyperthyroid individuals, levels of total hexosaminidase (730 ± 67 units) (mean ± S.D.) and isoenzyme A (516 ± 46) were significantly higher than levels found in either the hypothyroid (total: 547 ± 30; isoenzyme A: 352 ± 31) or euthyroid (total: 620 ± 81 A; isoenzyme A: 423 ± 45) groups. However, no change was observed in levels of isoenzyme B among hypothyroid (195 ± 19), euthyroid (197 ± 43) and hyperthyroid (215 ± 32) groups. These data substantiate our earlier findings in the rat, wherein thyroxine administration evoked a similar response in the liver. They are of particular interest in light of the deficiency of HEX A in variants of GM 2 gangliosidosis.