Endocrine Abstracts

Objective: To investigate whether routine assessment of free testosterone improves the diagnostic accuracy of functional male hypogonadism.

Methods: Total and free testosterone (calculated through SHBG assessment) were determined in 372 male patients (median age 44) referring to our department for sexual symptoms symptoms (188 patients) or infertility (184 men). Low total and free testosterone were defined as < 2.31 ng/ml and <63 pg/ml, respectively.

Results: Hypogonadism, as calculated free testosterone <63 pg/ml, was found in 47/188 (25.0%) patients with sexual symptoms and in 21/184 (11.4%) with infertility. Total testosterone determination misdiagnosed hypogonadism in 8.4% (12/143) of men with sexual symptoms and in 2% (3/152) with infertility. In subjects with borderline total testosterone (between 2.31 and 3.5 ng/ml), only 24.7% (19/77) had hypogonadism confirmed by free testosterone levels. No subjects had known conditions altering SHBG. Free testosterone levels significantly correlated with age, haematocrit, gonadotropins, gynecomastia, BMI, and number of co-morbidities, whereas total testosterone associated only with the latter two. Moreover age, haematocrit, erectile dysfunction, BMI, and low libido were significantly different between men with normal and low free testosterone, whereas only BMI and low libido were significantly different between patients with normal and low total testosterone.

Conclusion: This is the first study evaluating the impact of FT assessment to diagnose functional hypogonadism in men with hypogonadal symptoms or infertility. Routine assessment of free testosterone allows a more accurate diagnosis of functional hypogonadism, especially in men with sexual symptoms. Free testosterone levels associate with clinical and biochemical parameters of androgen deficiency better than total testosterone levels. A first-line assessment of SHBG and calculated free testosterone levels should be performed in all men with symptoms of male hypogonadism, to improve our diagnostic performance.