Age-related variations in thyroid function hormones indicate the risk of prostate cancer: evidence from a nationally representative dataset.

[BACKGROUND] The risk of prostate cancer (PCa) is closely related to age and influenced by endocrine hormone imbalances. The study aimed to discuss the association between thyroid function hormone variations across different age groups and PCa as well as prostate-specific antigen (PSA) levels.

[METHODS] We analyzed data from two National Health and Nutrition Examination Survey (NHANES) cycles (2007-2008, 2009-2010). Serum thyroid function tests were conducted using immunoenzymatic assays. PCa was identified through self-reported diagnosis, and highly-probable PCa was identified by elevated PSA (>10 ng/mL or 4-10 ng/mL with a PSA ratio <10%). Weighted multivariable logistic regression assessed the relationship between thyroid hormone levels and the risk of PCa and highly-probable PCa.

[RESULTS] Among 2,169 participants, the prevalence of PCa was 5.35%, higher in those aged ≥65 years (12.13%) compared to those <65 years (1.52%). Elevated total triiodothyronine (TT3) and free triiodothyronine (FT3) were significantly associated with increased PCa risk in older adults [TT3: odds ratio (OR) =1.481, P<0.001; FT3: OR =1.452, P<0.001]. Among those without PCa, elevated total thyroxine (TT4) and free thyroxine (FT4) were associated with higher highly-probable PCa, with TT4 indicating early risk in individuals younger than 65 years, and FT4 in those 65 years or older. Higher TSH levels were associated with increased PSA ratio, while TT3 and FT3 showed stronger inverse age-dependent associations with total and free PSA levels. FT4 was only negatively associated with PSA ratio in older adults.

[CONCLUSIONS] Thyroid function hormone levels were associated with PCa risk in older adults and also indicated an increased early risk of PCa in younger adults, as reflected by PSA markers.