Gonadal axis hormones in male schizophrenic patients during treatment with haloperidol and after switch to risperidone

Rationale: The atypical neuroleptic risperidone, in addition to its dopamine receptor blocking activity, has a high affinity for serotonergic receptors. Since both dopaminergic and serotonergic neuronal activities participate in regulation of the pituitary – gonadal axis (PGA), it is expected that a switch from treatment with haloperidol to treatment with risperidone should influence plasma levels of PGA hormones. Objective: To study the effects of a drug with dopamine and serotonin receptor blocking activity on PGA hormones in patients who were on treatment with a dopamine receptor blocker. Methods: Plasma levels of testosterone, luteinizing harmone (LH) and follicle stimulating harmone (FSH), as well as prolactin and cortisol, were measured in 16 male schizophrenic patients during treatment with haloperidol (mean dose 23.3 mg daily, SD = 16.9) and 6 weeks later after switching to treatment with risperidone (mean dose 11.8 mg daily, SD = 2.9). Psychopathology was assessed by BPRS. Results: After switching to risperidone, total BPRS score and the scores in its subscales for positive, negative, and general symptoms were all significantly reduced in the order of 35–45%. Prolactin levels were significantly increased from 39.5 ± 22.3 to 58.9 ± 28.5 ng/ml (F = 4.61, P = 0.04), while cortisol, testosterone, LH, and FSH remained unchanged. No significant correlations between prolactin increases and reduction in BPRS or in its subscale scores were found. Conclusions: The results show that blocking of both dopamine and serotonin receptors does not influence the pituitary – gonadal axis but considerably increases prolactin release. Received: 29 June 1998/Final version: 23 October 1998