Hypothalamo-pituitary dopaminergic system in patients with myotonic dystrophy

We studied the function of hypothalamo-pituitary dopaminergic system in 15 myotonic dystrophy (MyD) patients whose growth hormone (GH) responses to insulin or arginine had been normal. We obtained the following findings: (1) basal levels of plasma GH and prolactin (PRL) were normal, although the latter levels were slightly lower than controls, (2) both GH and PRL responses to L-dopa or bromocriptine were significantly blunted compared with controls, (3) PRL response to sulpiride was also significantly low compared with controls. These results indicate that hypothalamic dopaminergic neuron and its postsynaptic dopamine receptors relating to GH secretion might be impaired. It was also suggested that the dopamine receptors of pituitary PRL cells might be impaired and the PRL reserve of pituitary cells might be decreased in some case.