Within- and Across-Sex Inheritance of Bone Microarchitecture.

Context: The maternal heritability of bone microarchitecture according to the sex of the offspring is not known. Objective: To explore sex difference and influence of mother's menopausal status on the heritability of bone microarchitecture between mothers and their offspring. Subjects and Methods: In 102 mother-daughter and 161 mother-son pairs, volumetric bone mineral density (BMD) and bone microarchitecture were measured at the distal radius and tibia by high-resolution peripheral quantitative computed tomography. A principal components analysis was applied for the radius and the tibia volumetric BMD and microarchitecture parameters separately. Two components, a trabecular one and a cortical one were identified at the radius and tibia. Half heritability (½h2) was estimated as the slope of the regression between offspring and mothers for each bone parameter separately. Results: The mean age (± standard deviation) of mothers and daughters was 50.6 ± 4.1 years and 20.4 ± 0.5 years, respectively; that of mothers and sons was 45.8 ± 3.9 years and 15.2 ± 0.5 years, respectively. Most trabecular and cortical parameters were inherited in both mother-daughter and mother-son pairs (ß = 0.15 to 0.33; P = 0.05 to 0.001). At the tibia, trabecular and cortical principal components were significantly inherited in both sexes, whereas only the trabecular one was inherited at the radius (½h2, 21% to 35%). There was no difference in heritability of bone microarchitecture between mother-daughter and mother-son pairs. All heritabilities remained after adjustment for age, weight, height, gonadal status, and areal BMD (½h2, 9% to 25%). In the mother-daughter pairs, there was no systematic drop of heritability across menopause. Conclusions: Volumetric bone density and microarchitecture are highly and similarly inherited between and within sexes. The genetic effects remain predominant across menopause.