Hypothalamo-pituitary function and dopamine dependence in untreated parkinsonian patients

Altered prolactin and thyrotropin responses to the TRH test in parkinsonian patients are held to indicate an impairment of the tubero-infundibular dopaminergic axis (TIDA). We correlated the plasmatic prolactin (PRL), thyrotropin (TSH) and somatotropin (GH) responses to TRH and bromocriptine + TRH of 12 parkinsonian patients, who had never received anti-parkinsonian drugs, with the severity, the duration, the age of onset and the dopamine-dependence of the motor symptomatology as indicated by the therapeutic response to a six-month oral treatment with bromocriptine. Patients with basal motor impairment over 9 on the Webster Rating Scale (WRS), those with duration of the disease over 24 months and those with onset earlier than 55 years of age showed lower PRL responses than the respectively matched subgroups. Patients showing a therapeutic motor improvement over 50% on the WRS (dopamine-dependent or "responder") showed lower PRL and TSH and higher GH responses than the non-responders. These findings suggest that the TIDA impairment described in Parkinson's disease develops along with the progressive course of the extrapyramidal involvement and is strictly correlated with the dopamine-dependence of the motor impairment.