Bone Mass and Hormone Analysis in Patients With Spinal Cord Injury: Evidence for a Gonadal Axis Disruption

Abstract

CONTEXT: Bone loss is a constant finding in patients with spinal cord injury (SCI). OBJECTIVE: We sought to evaluate potential modifiable factors that could lead to bone loss in complete motor paraplegia by examining gonadal axis hormones, vitamin D status, and bone markers. DESIGN: This is a cross sectional. SETTING: It includes SCI Outpatient. PATIENTS AND OTHER PARTICIPANTS: Twenty-nine chronic male patients with SCI were compared with 17 age-matched, able-bodied men. MAIN OUTCOME MEASURE: The bone mineral density (BMD) of lower limbs and lumbar spine were measured using dual x-ray absorptiometry. Parathormone, 25-hydroxyvitamin D [25(OH)D], collagen type I C-terminal telopeptide (CTX), and sexual hormone were measured. RESULTS: Patients with SCI had lower BMD at the inferior limbs sites. CTX showed an inverse relationship with the time since injury. Patients had lower free T levels (SCI, 12.00 ± 2.91 vs controls, 19.51 ± 5.72; P ≤ .001), and the majority (72%) had normal/low levels of gonadotropins. Low T, however, was not related to low bone mass in patients with SCI. In the controls, the 25(OH)D level was positively correlated with the T and with the lumbar spine BMD, but these correlations were not observed in the SCI. CONCLUSIONS: Impairment of testicular function after SCI was indicated by the low levels of T and the loss of correlation between T and 25(OH)D levels; this correlation was present in the able-bodied controls. Inappropriate levels of gonadotropins were identified in most patients, featuring a hypogonadotropic hypogonadism and suggesting a disruption of the pituitary-gonadal axis. T concentrations might not be an effective target for bone loss therapy.