The thyroid and the kidney have well-documented connections. Thyroid hypofunction is related to decreased renal plasma flow (RPF), and hypothyroidism is common in chronic kidney illness; nevertheless, the thyroid-kidney axis in the euthyroid state is poorly understood. The purpose of this study was to look at the relationship between thyroid function and renovascular parameters in a well-phenotyped group of euthyroid, normotensive, and hypertensive people. The HyperPATH Consortium conducted this cross-sectional, multicenter investigation at five academic institutions in the United States and Europe. A total of 789 people aged 18 to 65 years old with blood thyrotropin levels ranging from 0.4 to 5.5 mIU/L took part; those with uncontrolled or secondary hypertension or using medication that affects the hypothalamus-pituitary-thyroid axis were excluded. In the context of a liberal and restricted salt diet, hemodynamic measures such as RPF, thyroid function tests, and the Thr92Ala deiodinase 2 polymorphism were evaluated. Researchers looked for links between thyroid function and renovascular measures while controlling for confounding variables including age, hypertension, and diabetes. Serum TSH was shown to be inversely related to RPF in both liberal and limited salt diet settings. When the study was limited to healthy young people, serum TSH remained an independent predictor of RPF on a high salt diet.

Serum TSH levels, but not fTI or the Thr92Ala D2 polymorphism, were independently inversely related with RPF in HyperPATH Consortium participants. These data imply a direct link between TSH and renovascular dynamics, even when TSH is within the normal range, and require further research.