Several studies have suggested that vitamin D and testosterone levels may be physiologically and pathologically interlinked. However this relsationship has not been studied in schizophrenia.

To demonstrate an association between vitamin D and testosterone levles in schizophrenia.

To establish that hypovitaminosis D is associated with hypotestosteronrmia.

Laboratory data of all male patients with schizophrenia seen for annual physicals in our office was reviewed. Vitamin D was measured as 25-hydroxyvitamin D and classified as follows: more than 30 ng/ml: normal; 21 to 30 ng/ml: mild deficiency; 11 to 20 ng/mL: moderate deficiency; 10 ng/ml or less: severe deficiency. Testosterone levels were tested by L/MSMS methodology (normal: 348.0–1197 ng/dL).

47 male patients had both vitamin d and testosterone measured: Of these 47, 36 (77%) had hypovitaminosis D and 20 (43%) had LTL. Of the 11 with normal vitamin d levels, 2 (18%) had LTL and 8 (82%) had NTL. Of the 36 with low vitamin D, 18 (50%) had LTL and 18 had NTL (50%). Of the 6 with severe deficiency, 4 (66%) had low and 2 had normal testosterone levels (NTL); of the 15 with moderate deficiency, 7 (47%) had LTL and 9 had NTL and of the 15 with mild deficiency, 7 (47%) had LTL and 8 had NTL.

Vitamin D deficiency appears to be closely related to low testosterone levels in a male schizophrenic population. Supplementation with both vitamin D and testosterone may be needed in these patients.