Effect of Altered Thyroid Function Upon Steroid Circadian Rhythms in Man1

Abstract

To further investigate the effect of altered thyroid function upon endogenous steroid metabolism, a study was undertaken of the circadian variation in plasma free, plasma conjugated and urinary 17-hydroxycorticosteroids (17-OHCS) in patients with hyperthyroidism and myxedema. Spontaneous hyperthyroidism or the administration of triiodothyronine accelerated the disappearance of free 17-OHCS from the plasma and exaggerated the circadian variation in plasma conjugated 17-OHCS. The converse of these results was observed in patients with myxedema. The retardation in metabolic transformation led to a more sustained elevation of plasma free 17-OHCS and a delay in the conversion to conjugated metabolites. The normal circadian variation in plasma conjugated 17-OHCS was not seen in the patients with myxedema. The pattern of urinary 17-OHCS excretion reflected the changes in plasma conjugated 17-OHCS.