PITUITARY EVALUATION IN PATIENTS WITH LOW PROSTATE-SPECIFIC ANTIGEN.

ABSTRACT

OBJECTIVE: To evaluate pituitary function in men with a low screening prostate-specific antigen (PSA) of ≤0.1 ng/mL and test the hypothesis that low PSA is associated with hypogonadism alone or other hormone deficiency. METHODS: This was a case-control study evaluating the rates of hypogonadism and low insulin-like growth factor (IGF)-1 in a cohort of men with low or normal screening PSA level. Sixty-four men >40 years old without known prostate disease were divided into a low-PSA group (PSA ≤0.1 ng/mL) and normal-PSA group (PSA 1 to 4 ng/mL). Hormonal evaluation included total testosterone, prolactin, luteinizing hormone, follicle-stimulating hormone, IGF-1, growth hormone, thyroid-stimulating hormone, free thyroxine, morning cortisol, and adrenocorticotropic hormone. The difference between each patient's observed IGF-1 and the IGF-1 age-specific lower limit was calculated. The odds ratios (ORs) for having hypogonadism and associated 95% confidence intervals (CIs) were calculated using the Cochran-Mantel-Haenszel test. RESULTS: The rate of hypogonadism was significantly higher in the low-PSA group (n = 44) compared with the normal-PSA control group (n = 20) (45.5% vs. 15.0%; OR, 4.7; 95% CI, 1.2 to 18.4; P = .027). The total testosterone in the low-PSA group was significantly lower compared with the control group (181.7 ng/dL vs. 263.7 ng/dL; P = .008). IGF-1 values were below their lower bound in 18.6% of subjects in the low-PSA group, compared with 0% in the control group. CONCLUSION: Men with low PSA have significantly higher rates of hypogonadism and low IGF-1 compared with those with normal PSA. In such men, we recommend hormonal evaluation to exclude associated pituitary dysfunction. ABBREVIATIONS BMI = body mass index; GH = growth hormone; IGF-1 = insulin-like growth factor 1; MRI = magnetic resonance imaging; PSA = prostate-specific antigen; T2DM = type 2 diabetes mellitus; VA-NWIHCS = VA-Nebraska Western Iowa Health Care System.