To the Editor:

Martina Hummer, M.D., et al. (1) reported the occurrence of low bone mineral density in a group of young male subjects with schizophrenia. Levine et al. (2) and Applebaum et al. (3) reported elevated plasma homocysteine levels in young male schizophrenic patients.

Elevated homocysteine plasma levels were recently reported to be associated with osteoporotic bone fractures in the elderly in two large follow-up studies (4, 5). McLean et al. (4) analyzed blood samples obtained and stored from 1,999 men and women as part of the long-term Framingham Study. These researchers found that men and women in the upper quartile of homocysteine concentrations were nearly four and two times, respectively, as likely to later have a hip fracture in comparison to the lower quartile of homocysteine concentrations. Van Meurs et al. (5) analyzed blood samples and health data from 2,406 people. Men and women in the upper quartile of homocysteine concentrations were about twice as likely to have a hip or other bone fracture as were those in the lower quartile of homocysteine concentrations.

The mechanism underlying homocysteine’s effect on bone metabolism is not yet clear. However, several mechanisms were suggested, including that elevated homocysteine disturbs the cross-linking of collagen in bone and disturbs osteoblast formation (6).

Thus, it is suggested that elevated homocysteine levels may be a mechanism of the low bone mineral density reported by Dr. Hummer et al. (1) among young male subjects suffering from schizophrenia.