Premium
ALTERED DOPAMINERGIC REGULATION OF THYROTROPHIN RELEASE IN PATIENTS WITH PROLACTINOMAS: COMPARISON WITH OTHER TESTS OF HYPOTHALAMIC‐PITUITARY FUNCTION
Author(s) -
SCANLON M. F.,
RODRIGUEZARNAO M. D.,
McGREGOR A. M.,
WEIGHTMAN D.,
LEWIS M.,
COOK D. B.,
GOMEZPAN A.,
HALL R.
Publication year - 1981
Publication title -
clinical endocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.055
H-Index - 147
eISSN - 1365-2265
pISSN - 0300-0664
DOI - 10.1111/j.1365-2265.1981.tb00608.x
Subject(s) - medicine , endocrinology , domperidone , dopaminergic , prolactin , hyperprolactinaemia , dopamine , prolactinoma , hormone
SUMMARY This study was carried out to test the hypothesis that sustained hyperprolactinaemia in patients with prolactinomas stimulates hypothalamic dopaminergic activity via a short loop positive feedback effect of prolactin (PRL). The intensity of dopamine (DA) effects on the pituitary around the adenoma was evaluated by measuring thyroid stimulating hormone (TSH) responses to intravenous injection of domperidone (10 mg) a new DA receptor blocking drug that does not penetrate the blood‐brain barrier. TSH responses have been compared with those of PRL to the same agent. Eight females with prolactinomas showed greater TSH release after domperidone than nine normal females (sum of TSH increments over 120 min 17·5 ± 1·7 v. 8·9±1·5 mu/l, P < 0·001) whilst PRL release was reduced (sum of PRL increments over 120 min 5·9 ± 2·4 v. 21·8 ± 3·8 mu/l ± 10 −3 , P < 0·01). Amongst nineteen hyperprolactinaemic females with apparently normal pituitary fossae (plain skull X‐ray), ten showed an exaggerated TSH response (ΔTSH, 4·2 ± 0·6 mu/l, range 2·5–9·40 mu/l) and reduced PRL response to domperidone, comparable with established tumour cases. In the remaining nine normal fossa hyperprolactinaemic females, the TSH and PRL responses to domperidone were similar to normal females. These results support the initial hypothesis and indicate the coexistence of a defect in the dopaminergic inhibition of PRL release and increased dopaminergic inhibition of TSH release in patients with prolactinomas. The presence of an exaggerated TSH response to DA antagonism in a euthyroid, radiologically normal (plain skull X‐ray), hyperprolactinaemic patient is compatible with the presence of an autonomously‐functioning, PRL secreting, pituitary microadenoma and the TSH changes seen in these patients after DA antagonist administration can be readily detected by sensitive TSH radioimmunoassay.