Changes in serum N-acetyl-β-hexosaminidase levels after treatment of hypothyroid and hyperthyroid individuals with l-thyroxine and propylthiouracil

Abstract

Multiple semm samples were obtained from six hypothyroid and six hyperthyroid females, 11–17 years of age, over the course of their corrective treatment with l-thyroxine (LT 4) and propylthiouracil (PTU), respectively. Sera were assayed for total N-acetyl- β-hexosaminidase (HEX), the A (heat-labile) and B (heat-stable) isozymes, and total T 4. HEX activity (total and HEX A) in sera from hypothyroid (< 4 μg/dl T 4) patients (total HEX: 518 ± 66 nmol/60 min/ml, mean ± S.D.; HEX A: 325 ± 55; n = 5) was significantly lower than that of the euthyroid control group (total HEX: 638 ± 77 ( p < 0.005); HEX A: 420 ± 76 ( p < 0.01); n = 23); no difference in HEX B levels was noted. Serum samples from patients successfully treated for hypothyroidism via oral administration of LT 4 ( n = 12) displayed levels of total HEX (722 ± 113) and HEX A (491 ± 91) significantly higher than those of the control group ( p < 0.01 in both cases); again, no change in levels of HEX B was observed. HEX activity in sera from hyperthyroid ( > 13 μg/dl T 4) individuals (total HEX: 839 ± 96; HEX A: 540 ± 74; HEX B: 299 ± 52; n = 20) was significantly higher than that of the control group ( p < 0.005 in all cases). The depression of hormone activity to the eythyroid range by PTU was accompanied by a decrease in enzyme activity to control levels (total HEX: 632 ± 92; HEX A: 400 ± 55; HEX B: 232 ± 52; n = 16). Non-parametric analysis of the data shows highly significant differences between pre- and post-treatment enzyme levels (α < 0.001) in both hyper- and hypothyroid groups. Alteration of thyroid status, and specifically T 4 levels is, therefore, indicated to be a contributing factor in the regulation of serum HEX activity in humans, as evidenced by individual responsiveness to oral administration of this hormone, or inhibitors of its peripheral metabolism.