Neuroendocrine responses to levodopa in multiple system atrophy (MSA)

Hypothalamic dopaminergic pathways are involved in the regulation of growth hormone and prolactin release from the anterior pituitary. Neuroendocrine studies in patients with multiple system atrophy (MSA), in whom there is a reported loss of hypothalamic dopamine, are few and contradictory. We therefore studied the neuroendocrine responses to 250 mg levodopa (plus 25 mg carbidopa) in subjects with MSA (n = 15), and compared them with age‐ and sex‐matched healthy control subjects (n = 8). There were no significant differences in basal or post‐levodopa levels of growth hormone (GH), growth hormone‐releasing hormone (GHRH), glucose, insulin‐like growth factor (IGF‐1), or thyroid‐stimulating hormone (TSH) between the groups. In patients with MSA, basal levels of prolactin were elevated (21.1 ± 5.2 ng/mL [mean ± standard error]) compared with control subjects (12.1 ± 1.7, p