Introduction: Leptin, adipocyte hormone and energy sufficiency signal to the hypothalamus, has many regulatory functions including bone growth controlled through the sympathetic nervous system (SNS) and peripherally. In AIS girls, we attribute several skeletal asymmetries associated with lower BMI to asymmetric SNS function created by hypothalamic dysfunction (upregulation) resulting from hormesis as an abnormality of a putative normal leptin-hypothalamic-SNSdriven mechanism. Hormesis is a bimodal dose response of cells, or organisms, to an exogenous (eg drug or toxin), or intrinsic factor (eg hormone), in which the factor induces stimulatory or beneficial effects at low doses and inhibitory or adverse effects at high doses.
Objectives: Dr EJ Calabrese recommended testing for hormetic effect in AIS girls using BMI as a surrogate measure for leptin as the “dose”, and evaluating skeletal growth asymmetries of AIS as the adverse effect.
Materials and Methods: Data from girls with right thoracic (n=110) and lower spine scoliosis (thoracolumbar and lumbar, n=64) are evaluated for skeletal asymmetries in relation to BMI – Cobb angle (CA), apical vertebral (AVR), upper arm length asymmetry (UALA) and iliac height asymmetry (IHA)(Spearman's rho, ñ).
Results: RT scoliosis. AVR (p=0.007, ñ=0.257), but not CA or UALA correlates significantly with BMI, Lower spine scoliosis. AVR (p=0.012, ñ=0.311) and IHA (p=0.046, ñ=0.250) but not CA correlate significantly with BMI.
Conclusion: These left-right skeletal asymmetries increase with increase of BMI, and possibly with increase in circulating leptin levels (dose).
Significance: The findings are consistent with leptin having a hormetic effect in AIS girls.