Testosterone Levels for Evaluation of Androgen Deficiency

A 54-year-old man with hypertension and diabetes presented to the endocrinology clinic with a 5-month history of fatigue, weight gain, interrupted sleep, and daytime somnolence. He has normal libido but experiences occasional erectile dysfunction, which is being successfully managed with a phosphodiesterase-5 inhibitor. His other medications include metformin and amlodipine. He is married, has 3 children, and reports a sedentary lifestyle. He recently heard on the radio that his symptoms might be due to “low T.” One month ago, he saw his primary care physician and requested measurement of his testosterone level. His morning total testosterone level (measured by mass spectrometry) was 279 ng/dL (normal reference range for this laboratory, 300-900 ng/dL), prompting his referral. On physical examination, his body mass index was 34.7 (calculated as weight in kilograms divided by height in meters squared).He was not cushingoid and his visual fields were normal. Acanthosis nigricans was noticed on the neck. There was no gynecomastia. His testes were normal in size. His muscle strength was normal. Relevant laboratory tests, including repeat morning total testosterone assessed in an endocrinology clinic, are reported in Table.