The Relationships between Thyroid Hormone Levels and Lower Urinary Tract Symptoms/Benign Prostatic Hyperplasia

PURPOSE: We examined the association between thyroid hormone and lower urinary tract symptoms (LUTS)/benign prostatic hyperplasia (BPH). MATERIALS AND METHODS: A total of 5,708 middle aged men were included. LUTS/BPH were assessed using the international prostate symptom score (IPSS), total prostate volume (TPV), maximal flow rate (Qmax), and a full metabolic workup. Thyroid stimulating hormone (TSH) and free thyroxine (FT4) levels were measured using chemiluminescence immunoassay. We divided participants into quartiles based on their TSH and FT4 levels: first to fourth quartile (Q1–Q4). RESULTS: There was a significant increase in the percentage of men with IPSS>7, Qmax<10 mL/s, and TPV≥30 mL with increase of FT4 quartile. The adjusted odds ratio (OR) for TPV≥30 mL and IPSS>7 were significantly different between FT4 quartile groups (ORs; [5–95 percentile interval], p; TPV≥30 mL, Q1: 0.000 [references]; Q2: 1.140 [0.911–1.361], p=0.291; Q3: 1.260 [1.030–1.541], p=0.025; Q4: 1.367 [1.122–1.665], p=0.002; IPSS>7: Q1: 0.000 [references]; Q2: 0.969 [0.836–1.123], p=0.677; Q3: 1.123 [0.965–1.308], p=0.133; Q4: 1.221 [1.049–1.420], p=0.010). In men with above median levels of testosterone, the FT4 correlated positively with TPV, even after adjusting for confounders. However, the FT4 was not correlated with TPV in men with below median levels of testosterone. TSH was not related to LUTS/BPH measurements. CONCLUSIONS: TPV, IPSS, and Qmax were significantly related to FT4. TPV and IPSS were significantly and independently related to FT4. Additionally, the relationship between FT4 and TPV was distinct when testosterone levels are high.