Hyperprolactinemia can inhibit sex steroids, resulting in bone loss. We, thus, set out to evaluate the effect of risperidone-induced hyperprolactinemia on bone mineral density in youth.

Children and adolescent males treated with risperidone for a minimum of six months underwent volumetric bone mineral density (vBMD) measurement using peripheral quantitative computerized tomography of the ultra-distal nondominant radius. Their treatment history was reviewed and their prolactin and testosterone serum levels measured.

We recruited 73 males (mean age: 12.1yrs [SD=2.9], mean Tanner stage: 2.6 [SD=1.4]) treated with 0.03mg/kg (SD=0.02) of risperidone per day for an average of 3.1yrs (SD=1.9). Hyperprolactinemia (defined as a prolactin level > 18.4ng/ml) was present in 51% of the sample. After controlling for Tanner stage which was strongly associated with serum testosterone, we found a trend for a negative effect of prolactin on testosterone. As expected, ultra-distal radius cross-sectional area and cortical vBMD, but not trabecular vBMD, increased with pubertal development. After adjusting for prolactin and pubertal stage, in the subgroup of peri/pubertal (i.e. Tanner stage ≥ 2) participants with hyperprolactinemia, prolactin was negatively associated with trabecular, but not cortical, vBMD.

To our knowledge, our data are the first to describe the negative effect of risperidone-induced hyperprolactinemia on bone mineral density following long-term treatment in youth.