Endocrine Abstracts

Microprolactinomas are considered not to cause pituitary hormone dysfunction, but there is little data available on the prevalence of hormone deficiencies. We aimed to establish the frequency of pituitary hormone dysfunction in patients with hyperprolactinaemia.

We examined the casenotes of 124 consecutive patients (85 females) with documented hyperprolactinemia from our pituitary data-base. 52 patients had macroadenomas (tumour > 1cm diameter), 64 microadenomas (tumour < 1 cm, or clinical diagnosed), 3 medications-related, 5 macroprolactinemia.

Of 64 patients diagnosed to have microprolactinoma, MRI, identified a microadenoma in 31/59. 17 patients with positive MRI had dynamic pituitary testing which showed combined growth hormone (GH) and ACTH deficiencies in 1 patient and ACTH deficiency in one patient. 16/28 MRI negative patients, all medically treated, had dynamic pituitary testing with 1 patient exhibiting GH deficiency alone, 2 GH and ACTH deficiencies and 2 ACTH deficiency alone. 1 patient with MRI positive microprolactinomas had cranial diabetes insipidus.

This study shows a significant incidence (7/33, 21%) of GH and glucocorticoid deficiency in surgically naive patients with microprolactinomas. 2/17 patients with tumour identified by imaging had GH/ACTH deficiency, compared with 5/16 with normal imaging. We conclude that patients with microprolactinoma may have other abnormalities of pituitary hormone secretion, particularly those with normal MRI imaging. This suggests that some patients with hyperprolactinaemia and normal MRI pituitary may have non-tumour pituitary disease. We suggest that dynamic pituitary testing should have a wider role in the assessment of pituitary function in patients with hyperprolactinaemia.