Objective: To determine the effects of estrogen deprivation on bone mass in young women in whom large bone mass increases are known to occur.
Methods: Over 2 years, nine amenorrheic and 21 normal women were studied, classified into exercising (dancers) and sedentary subjects. An integrated estrogen exposure score was used to determine estrogen response during the 2 years of study. Bone mineral density was measured by single and dual photon absorptiometry in the spine, wrist, and foot (metatarsus).
Results: Hypoestrogenism was present in all amenorrheic women in the first year, and mean estrogen exposure scores were lower in these subjects during the 2 years. Mean spine, wrist, and metatarsal bone mineral density measurements were lower in the amenorrheic women and remained below the levels in controls, despite changing clinical indices and return of menses in some of the subjects. Amenorrheic dancers showed the greatest increase in spine bone mineral density, gaining 9.65% in the first year, 4.49% in the second, and an increase of 14.43% (P < .05) over the total period. Their bone mineral density values, however, remained significantly below those of normal controls during the duration of the study. The most significant gains were seen in two subjects with weight gain and return of irregular periods (three periods in 12 months).
Conclusion: Young amenorrheic exercising women appear to increase bone mass before the return of normal menses; however, bone mass remained below control values during 2 years of study, possibly because of long-term adolescent hypoestrogenism.