Because thyroid hormone has numerous effects on the kidney, heart, and vascular system, thyroid dysfunction can cause significant changes in renal and cardiovascular functions (1–3). In particular, hypothyroidism is known to be associated with reduced renal plasma flow (RPF) and low glomerular filtration rate (GFR)
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3313737/