NASHVILLE, TENN.– Checking free testosterone and prolactin levels can help identify which men with secondary hypogonadism should get brain MRIs.
If the levels are normal, it’s unlikely that hypothalamic-pituitary imaging will reveal a medically significant pituitary abnormality. “However, MRI is warranted in men with high prolactin or very low free testosterone [because] both are associated with pituitary structural abnormalities,” said lead investigator and medical resident Dr. Cong Santoso of Wright-Patterson Air Force Base Medical Center in Dayton, Ohio.
M. Alexander Otto/Frontline Medical News
Dr. Cong Santoso
Dr. Santoso and her associate, Dr. Thomas Koroscil of Wright State University, Dayton, reviewed the charts of 88 men with secondary hypogonadism, all of whom had gotten an MRI, which in many places was once a routine investigation for the problem. Men with known pituitary lesions, pituitary apoplexy, infiltrative diseases, infections, or glucocorticoid use were among those excluded from the study.
A total of 16 men (18%) had abnormal MRIs. Adenomas were found in nine (10%) and empty sellas in seven (8%). Men with pituitary adenomas had significantly lower free testosterone (FT), compared with those who had normal MRIs (18.7 pg/mL vs. 36.4 pg/mL). Men with empty sella syndrome had significantly higher prolactin (PRL), compared with men who had normal MRIs (21.4 ng/mL vs. 11.2 ng/mL), Dr. Santoso reported.
There was no difference in levels of follicle-stimulating hormone or luteinizing hormone. There was a trend towards lower total testosterone in men with structural abnormalities, but it was not significant, probably because of the low numbers in the study, Dr. Santoso said at the annual meeting of the American Association of Clinical Endocrinologists.
At 16%, the incidence of pituitary imaging abnormalities was not greater than the prevalence of abnormalities in the general population, “indicating that there is little value to routinely obtain MRI in the evaluation of men with secondary hypogonadism” when FT and PRL are normal, she said.
Endocrine Society guidelines for secondary hypogonadism in men note that “the diagnostic yield of pituitary imaging to exclude pituitary and/or hypothalamic tumor can be improved by performing [MRIs] in men with serum testosterone less than 150 ng/dL, panhypopituitarism, persistent hyperprolactinemia, or symptoms of tumor mass effect.”
The findings from Dr. Santoso’s study add to that advice by suggesting a role for FT and by pinning high PRL and low FT to particular structural abnormalities. “We are adding to the guidelines to make them” stronger, she said.
About 70 men (80%) had type 2 diabetes or metabolic syndrome, both of which are associated with secondary hypogonadism, but they had no endocrinologic differences, compared with the other men.
Endocrinologists at Dr. Santoso’s institutions have moved away from routine MRIs in men with secondary hypogonadism and are relying more on lab values to indicate when MRIs are needed, she said.
There was no outside funding for the work, and Dr. Santoso had no disclosures.