Diagnostic Approach to Low Testosterone in Males

Initial Evaluation

• Serum prolactin levels should be measured in patients with low testosterone levels combined with low or low/normal luteinizing hormone (LH) levels to screen for hyperprolactinemia, which can indicate the presence of pituitary tumors such as prolactinomas 1, 2, 3
• Confirm low testosterone with at least two morning measurements showing levels consistently <300 ng/dL 4
• Measure LH levels to determine the etiology of testosterone deficiency 1, 2

Diagnostic Testing

• Check prolactin levels if LH is low or low/normal 3, 5
• Non-secreting adenomas may be present, as indicated by elevated prolactin levels 3, 6

Clinical Management

• If prolactin is elevated, repeat measurement to ensure the elevation is not spurious, and persistently high levels warrant referral to an endocrinologist 3, 5
• Consider pituitary MRI, especially if testosterone <150 ng/dL with low/normal LH 3
• Men with total testosterone levels <150 ng/dL and low/normal LH should undergo pituitary MRI regardless of prolactin levels, as non-secreting adenomas may be present 3