Subclinically low BMD in young men is associated with compromised bone microarchitecture and lower lean mass

Optimizing bone mass accrual early in life is a strategy for mitigating fracture risk in older age.

This study aimed to identify factors associated with lower than expected bone mass in healthy young adult men.

Data from 39 male participants (21 areal bone mineral density [aBMD] Z scores <-1.0 at either the total hip, femoral neck, or lumbar spine [Lower]; 18 Z scores ≥1.0, but not <-1.0 at any site [controls; Con]) were analyzed from a larger study. aBMD and body composition were assessed by dual-energy x-ray absorptiometry (DXA), and bone quality was evaluated at the tibia using high resolution-peripheral quantitative computed tomography (HR-pQCT). Fasted concentrations of bone turnover markers, testosterone, estradiol, parathyroid hormone (PTH), insulin-like growth factor-1 (IGF-1), and insulin-like growth factor-1 binding protein 5 (IGFBP-5) were measured via enzyme-linked immunosorbent assays.

The Lower group was older (age in years: Lower 25 [6]; Con 21 [5]; P = .037), shorter (m; Lower 1.74 [0.10]; Con 1.79 [0.10]; P = .024), and had less lean mass than Con (kg; Lower 54.2 [6.2]; Con 60.3 [6.9]; P = .018). Tibial bone microarchitecture (trabecular number 1/mm; Lower 1.7 [0.2]; Con 1.9 [0.2]; P = .004; trabecular separation mm; Lower 0.6 [0.1]; Con 0.5 [0.1]; P = .002) and strength (stiffness kN/mm Lower 207.7 [43.3]; Con 274.7 [39.7] and failure load kN Lower 11.3 [2.2]; Con 14.8 [2.0]; P < .001) were compromised in Lower. Alkaline phosphatase was greater (Lower 1528.2 [933.8]; Con 605.4 [624.1]; P = .003), and IGF-1 (Lower 265.5 [93.6]; Con 340.4 [106.5]; P = .027) was lower in Lower. Osteoblast activity (P ≥ .361) and gene expression were similar between groups (P ≥ .451).

Men with relatively lower than expected aBMD demonstrated compromised bone microarchitecture and lower lean mass, indicating the importance of targeted intervention for lean mass accrual during young adulthood.