Prolactin secretion in myotonic dystrophy.

In order to evaluate prolactin secretion in females with myotonic dystrophy (MD) prolactin responses to TRH, metoclopramide and bromocriptine were studied in 13 women with myotonic dystrophy (10 normoprolactinaemic and 3 hyperprolactinaemic) and 8 healthy women. Following TRH administration mean maximal net increase was significantly higher in a group of normoprolactinaemic patients with MD in comparison to controls (p less than 0.05). In three patients with increased basal prolactin levels an exaggerated prolactin response to TRH has been observed. Normal prolactin response in a group of normoprolactinaemic as well as in hyperprolactinaemic patients have been observed following metoclopramide bolus injection. Following bromocriptine administration, maximal net decrease in prolactin levels has been found to be greater in normoprolactinaemic patients compared to healthy subjects, although the difference was statistically insignificant. The suppressive action of bromocriptine was more pronounced in patients with hyperprolactinaemia. Those results showed that there is some derangement in prolactin secretion in myotonic dystrophy leading to increased prolactin levels in some patients. Although the mechanism of this derangement has not been clarified yet it seems that it is not mediated via dopaminergic receptors.