Article Text

PDF

The importance of reverse triiodothyronine in hypothyroid children on replacement treatment.
  1. M Desai,
  2. A J Irani,
  3. K Patil,
  4. C S Pandya

    Abstract

    Reverse triiodothyronine (rT3), triiodothyronine (T3), thyroxine (T4), and thyroid stimulating hormone (TSH) values were measured by radioimmunoassay in 40 children with congenital hypothyroidism who were being given levothyroxine (0.05-0.35 mg/day) and in 14 normal controls. In 15 of the children with hypothyroidism the treatment, judged by serum T4 and TSH values and thyrotrophin releasing hormone (TRH) test, seemed to be adequate and their mean rT3 value and rT3:T4 ratio were comparable with the controls. The remaining 25 children had a raised serum T4 and a low TSH value. Only 4 (16%) of these children had an abnormally high T3 concentration but the rT3 value was raised in 23 (92%) and their mean rT3 value and rT3:T4 ratio were significantly higher than in the control children. Less than 20% of this 'overtreated' group, however, had clinical hyperthyroidism. We suggest that in patients on T4 replacement treatment the peripheral thyroid homeostatic mechanisms produce larger amounts of rT3, thereby preventing high T3 values where serum T4 values are raised. This may explain why the 'overtreated' children showed no clinical evidence of hyperthyroidism. These findings emphasise the protective and selective role of peripheral monodeiodination.

    Statistics from Altmetric.com

    Request permissions

    If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.