Endocrine Abstracts

Background: Generally Endocrinologists strive to diagnose conditions biochemically prior to radiological investigation. Pituitary incidentalomas are observed in 10% of pituitary MRIs and together with stress induced hyperprolactinaemia, 10–20% of patients receive dopamine agonists (DAs) without a definite diagnosis. Menstrual imbalance is a common symptom of hyperprolactinaemia which can have multiple origins (e.g. hypothalamic, pituitary or ovarian). DAs have side effects including nausea, postural symptoms and rarely impulse control disorders. Cardiac valvulopathy has been reported at higher doses. The metoclopramide test (MT) provides a cheap and effective way of providing a biochemical diagnosis. Metoclopramide is a potent D2 dopamine antagonist; abnormal prolactin and TSH responses support a diagnosis of microprolactinoma or ‘disconnection hyperprolactinaemia’ due to larger pituitary lesions.

Aims & Method: To assess the usefulness of the MT in determining the aetiology of hyperprolactinaemia. The MT is done after excluding macroprolactin and clear cases of prolactinoma (PRL >2000 mU/l with classic symptoms). Retrospective study of patient’s who underwent MT (June’08–Mar’18) at a teaching hospital. Data were collected from electronic records.

Results: Hundred patients were included (34 male). Sixty one patients had MT suggestive of microprolactinoma, 57 underwent MRI pituitary with four conceiving whilst awaiting MRI on DA’s. 23/57 showed no adenoma and 21/57 had adenoma <5 mm, they were treated with DA’s as presumed microprolactinomas. Thirty-one patients had normal response to MT. 10/31 had MRI, four had pituitary adenoma <10 mm, thought to be incidentalomas.MT influenced management of 79/92 patients.

Conclusions: MT confirmed the aetiology of hyperprolactinaemia in all our patients and influenced management in 85%.We propose that there is utility of dynamic testing with MT in selected patient groups (absence of symptoms; prolactin <1000 mu/l & uncertainty regarding symptoms and negative MRI but classic symptoms). This would avoid treatment with DA’s in patients with stress hyperprolactinaemia or pituitary incidentalomas.

Reference

Sawers, Bevan et al., Clinical endocrinology 1997 46, 321–326