URINARY EXCRETION OF THYROXINE AND TRIIODOTHYRONINE IN DIFFERENT THYROID FUNCTION STATES IN MAN

Publisher Website
Google Scholar
Abstract
Urinary thyroxine (T4) and triiodothyronine (T3) have been measured by radioimmunoassay using trapping and separation on small Sephadex® columns. Serum concentrations of total and free T4 and T3 and endogenous creatinine clearance was also estimated. In 67 euthyroid controls the 24 h urinary T4 excretion varied in parallel with age dependent changes in renal function from mean 1788 to 1051 ng. Urinary T3 also decreased with age from mean 635 to 280 ng/24 h. Mean urinary clearance of T4 varied from 40.4 to 22.1 ml/min and T3 clearance from 160 to 107 ml/min parallel with creatinine clearance. The corresponding mean creatinine clearance values varied from 95 to 57 ml/min. In 24 hyperthyroid patients urinary T4 and T3 were highly increased, dependent on elevated free hormones in the serum to mean 3505 and 3865 ng/24 h. The corresponding T4 and T3 clearance mean values were 16.7 and 90.0 ml/min. In 7 untreated hypothyroid patients very low urinary T4 and T3 values were found on average 139 and 60 ng/24 h. Estimation of urinary thyroid hormones can be used for diagnostic purposes but is of limited practical importance. The physiology of thyroid hormone excretion in urine is complex. Both hormones are excreted by glomerular filtration of free hormones including tubular excretion and reabsorption.

This publication has 3 references indexed in Scilit: