Endocrine Abstracts

This study is designed to test the hypothesis that the gonadotrophin

responses to GnRH are heterogeneous and that, in pituitary/parapituitary lesion patients, the test is of no value as a diagnostic discriminator.

We carried out a 5-year retrospective review of GnRH results from a cohort of 104 male (46) and female (premenopausal 49, post-menopausal 9) patients with pituitary/parapituitary lesions. Serum LH and FSH levels were measured at baseline

and at 20 and 60 minutes after an iv bolus of 100 micrograms GnRH. The study

population was classified into non-functioning adenomas (NFA) (21 patients),

prolactinomas (41), somatotrophadenomas (9), gonadotrophinomas (6), corticotrophadenomas (6), and 'other', which included pituitary apoplexy, idiopathic hypopituitarism, craniopharyngiomas and optic nerve gliomas (21). Tumour was present on imaging of 99 patients: microadenomas (12),

macroadenomas (68), invasive macroadenomas (8) and other (11). Of the 104 patients investigated with this test, 96 patients were clinically or biochemically hypogonadal. There were 58 normal LH responses (3x the basal

LH value) compared with 34 for FSH (2x the basal FSH value), 29 subnormal LH

responses compared with 68 for FSH and 17 exaggerated LH responses (more

than 12 x basal LH or FSH values) compared with 2 exaggerated responses for

FSH. The GnRH responses were heterogenous, apart from the male NFA subgroup

(10 patients-1 was clinically hypogonadal and 5 were biochemically

hypogonadal), which all demonstrated subnormal LH responses, 1 normal FSH

response and 9 subnormal FSH responses.

We conclude that the GnRH test may be of value in the differential diagnosis

of non-functioning adenomas from other pituitary/parapituitary lesions.