Medical Therapy of Macroprolactinomas in Males: I. Prevalence of Hypopituitarism at Diagnosis. II. Proportion of Cases Exhibiting Recovery of Pituitary Function

Hyperprolactinaemia frequently causes secondary hypogonadism through central suppression of gonadotropin secretion. Macroprolactinomas (> 1 cm diameter) are more common in males and may additionally cause more generalised hypopituitarism. Recovery of the thyrotropic and/or corticotropic axes is well described following selective adenomectomy, but remains poorly defined in relation to medical (dopamine-agonist) therapy of macroprolactinomas. We therefore performed a retrospective examination of case records of male patients who had received medical therapy alone for macroprolactinoma between 1980-2001 (n = 35) and in whom tumor shrinkage was documented by interval pituitary imaging (reported throughout by a single neuroradiologist). Mean prolactin level at baseline was 59,932 mU/L (median 31,400; range 3,215-332,000); mean period of follow up was 4.2 years (median 2.6; range: 1.0-15). Defects of the following axes were evident at diagnosis: LH/FSH-testosterone (n = 27; 77%), TSH-T4 (n = 14; 41%-not including one case with pre-existing 1 degress hypothyroidism), ACTH-cortisol (n = 8; 23%). Overall, 14 men (40%) were deficient in 1 axis, seven (20%) in 2 axes and seven (20%) in 3 axes. Growth hormone secretory status was not systematically evaluated. In all but 6 patients, prolactin levels fell to normal or near-normal levels (mean 764 mU/L; median 260; range: < 10-4,833). Of the patients in whom adequate reassessment had been performed, thyrotroph function recovered in 4/9, corticotroph function in 4/6 and gonadotroph function in 16/26 cases. In four cases (11%) previously described, development of visual impairment as a result of the chiasmal traction syndrome necessitated a dose reduction in medical therapy to allow a degree of controlled tumor re-expansion. The prevalence at diagnosis of TSH and ACTH deficiency in men with macroprolactinomas was 41% and 23%, respectively. Among eight patients with insufficiency of TSH and/or ACTH secretion who underwent complete interval reassessment over several years of treatment, recovery of at least one axis occurred in six cases (75%). This study highlights the importance of screening ACTH- and/or TSH-deficient men during dopamine agonist therapy in order to identify cases where hypopituitarism has resolved.