Clomiphene in the evaluation of the pituitary-gonadal axis in acromegaly

Central Hypogonadism: Distinguishing Idiopathic Low Testosterone from Pituitary Tumors

OBJECTIVE

To attempt to determine clinical or hormonal characteristics that could help distinguish benign idiopathic low testosterone (ILT) from pituitary tumor.

METHODS

On retrospective review of medical records of patients encountered by Johns Hopkins endocrine staff between 1985 and July 1995, 64 patients who fulfilled our enrollment criteria--27 men with ILT and 37 patients with imaging-proven pituitary tumor--were identified. Men 21 years of age or older needed to have had serum testosterone, luteinizing hormone (LH), follicle-stimulating hormone (FSH), and prolactin levels measured before hormonal replacement therapy or pituitary tumor extirpation (or both) and a high-quality imaging scan (computed tomography or magnetic resonance imaging) done and interpreted by the Johns Hopkins radiology staff.

RESULTS

In comparison with men who had ILT, men with pituitary tumors had similar serum testosterone levels and significantly higher serum levels of LH, FSH, and prolactin. In addition, significantly more men with pituitary tumors had visual field abnormalities, headaches, and symptoms of hypothyroidism in comparison with the men with ILT. In contrast, the group with ILT complained significantly more of impotence, erectile dysfunction, and depression than did the group with pituitary tumors. The age at initial assessment was comparable in both study groups.

CONCLUSION

Although age at initial manifestation did not predict the presence of pituitary tumor, the group of men with tumors were more likely than those with ILT to have serum testosterone levels <150 ng/dL, higher serum gonadotropin and prolactin levels, and visual field abnormalities and less likely to have sexual dysfunction. Therefore, on the basis of our data, we recommend that men with these findings should be referred for a magnetic resonance image to exclude the presence of a tumor.

Pituitary-testicular function in acromegalic and hypophysectomized patients

Serum testosterone, LH, and FSH before and after i.v. injection of LHRH were studied in ten acromegalic men and in twenty-one males after hypophysectomy. Controls were normal men matched according to age. Compared to the controls, basal FSH was slightly higher and basal LGH slightly lower in the untreated acromegalics. The differences were not statistically significant. Serum testosterone and the ratio between basal FSH and LH were significantly lower in the patients. Following hypophysectomy because of acromegaly, the values were essentially unchanged. Hypophysectomy because of a functionless chromophobe adenoma resulted in a significantly lower maximum value of LH but not of FSH after LHRH. The results show that hypogonadism in acromegaly might be a result of imbalance between LH and FSH. They furthermore demonstrate that testing the pituitary-testicular function with LHRH in patients with pituitary disorders seems to be of limited value.