The value of pituitary magnetic resonance imaging in men with hypogonadism

We assessed the usefulness of magnetic resonance imaging (MRI) of the brain in the evaluation of hypogonadal men with a variety of endocrine patterns.

A total of 51 men with low levels of total testosterone (TT) or free testosterone (FT) underwent MRI. Erectile dysfunction and/or decreased libido were present in 43 (84.3%) of cases and infertility in 8 (15.7%). Serum prolactin (PRL) was obtained in all cases. Low levels of TT and FT were defined as less than 300 and 1.5 ng/dl, respectively. Markedly low levels of TT were defined as less than 200 ng/dl.

In 38 of 51 (74.5%) men the MRI was normal. A small pituitary gland (the partially empty sella syndrome) was noted in 9 (17.6%) cases and microadenoma was noted in 4 (7.8%). Prolactin levels were greater than twice the upper limit of normal in 3 of 4 (75%) cases of adenoma, and low FT was noted in all 4 cases. An additional case of adenoma was identified in a man with markedly decreased TT and normal PRL. All men with adenoma presented with the combination of erectile dysfunction and decreased libido. Among men without adenomas the highest PRL value was always less than twice the upper limit of normal. Overall, only 1 of 17 men with markedly decreased TT (less than 200 ng/dl) demonstrated adenoma. None of the 17 men with low luteinizing hormone with low TT or FT had an adenoma or pituitary/hypothalamic mass.

The likelihood of identifying pituitary adenoma by MRI is high if PRL levels are more than twice the upper limit of normal. Medically significant abnormalities are identified in only a small percentage of hypogonadal men with low luteinizing hormone or if TT levels are markedly decreased. The decision to obtain MRI in these latter cases should be based on individual circumstances.