Interrelationships among blood pressure, renal function, thyroid activity and renal thyroid depressing factor in...

Renal hypertension in rats was accompanied by both a decrease in thyroid activity (i.e., decreased total serum triiodothyronine concentration, increased serum thyroid-stimulating hormone concentration and increased thyroid weight) and renal function (i.e., reduced renal concentrating ability, increased blood urea nitrogen and serum creatinine concentrations). Systolic blood pressure, thyroid activity and level of renal function of individual hypertensive rats correlated significantly with the content of a thyroid-depressing factor in their kidneys. The results suggest, but do not prove, that a factor released by the kidneys during elevation of blood pressure and/or reduction in renal function may reduce thyroid function in the rat.