Association between Serum Total Testosterone Level and Bone Mineral Density in Middle-Aged Postmenopausal Women

Table 4

Threshold effect analysis of serum total testosterone level (ng/dL) on lumbar bone mineral density (mg/cm²) using two-piecewise linear regression model.

Lumbar bone mineral density	Adjusted β (95% CI), value
Serum total testosterone level
Fitting by standard linear model	1.07 (0.17, 1.97) 0.020
Fitting by two-piecewise linear model
Inflection point	30 (ng/dL)
Serum total testosterone level <30 (ng/dL)	1.47 (0.19, 2.75) 0.025
Serum total testosterone level >30 (ng/dL)	0.14 (−2.15, 2.44) 0.903
Log likelihood ratio	0.386

Age, race, body mass index, education level, income to poverty ratio, moderate activities, age since menopause, blood urea nitrogen, serum uric acid, total protein, serum phosphorus, and serum calcium were adjusted.