Endocrine Abstracts

Introduction: Studies suggest that schizophrenia and prolactin raising antipsychotics, one of them being risperidone, may be associated with low bone mass. On the other hand, weight gain as a consequence of antipsychotics in these patients may be the protective factor against osteoporosis.

Objective: Determine bone remodeling parameters and bone mass in patients with schizophrenia treated with long-acting injectable risperidone (LAIR) under naturalistic conditions.

Patients: Twenty-six out-patients with controlled schizophrenia (age 31.3±1.3 years; BMI 28.1±1.0 kg/m²) on maintenance therapy with LAIR for mean 18.0±1.6 months (range 6–36 months) with mean dose 38±2 mg. Thirty-five subjects matched by sex, age, BMI and education served as healthy controls.

Methods: Serum osteocalcin, C-terminal telopeptide of type I collagen (CTx), vitamin D, prolactin, sex steroids and PTH were assessed. Bone mineral density (BMD) was measured by dual-X ray absorptiometry at lumbar spine (LS) and femoral neck (FN).

Results: Osteocalcin did not differ between patients with schizophrenia compared with healthy subjects, while serum CTx was significantly higher in patients with schizophrenia (P=0.023). Patients with schizophrenia had lower LS BMD and LS Z-scores than healthy subjects, but not statistically significant (P=0.094, P=0.072 respectively) while at femoral neck (FN) there was no difference between two groups. Vitamin D deficiency was prevalent in patients with schizophrenia. Hyperprolactinemia was detected in 85% of patients, more commonly in females than males (all females and 67% males). Serum estradiol levels were lower in female patients than in healthy female subjects (P=0.001), while serum testosterone in males showed no significant differences (P=0.675). The percentage increase in body weight for all patients with schizophrenia on LAIR therapy was 4.7±1.5%.

Conclusion: Despite weight gain long-term administration of LAIR increased bone resorption marker CTx possibly through hyperprolactinemia-induced hypogonadism and/or possibly by decreasing brain serotonin activity. Brain serotonin has been recently shown to increase bone accrual and influence weight.