Development of a Model of Functional Endocrine Age in Japanese People

Objective: As the concentrations of some hormones are known to decrease with age, the aim of the present study was to develop a method to predict the functional age of the endocrine system.Methods: We retrospectively examined data for blood serum or plasma hormone concentration from 3,313 healthy Japanese (2,006 men and 1,307 women, aged 40-79 years) who gave blood samples between 2005 and 2009. Data for DHEA-s, insulin-like growth factor (IGF-I), cortisol, thyroid-stimulating hormone (TSH), free triiodothyronine (FT3) and free thyroxine (FT4) were analyzed, and the correlation between concentration of each hormone and age was calculated. In a second stage, data were grouped in 10-year age intervals, subjected to one-way analysis of variance (ANOVA) and evaluated using Tukey’s post-hoc test.Results: In both men and women, TSH was positively correlated with age. IGF-I, DHEA-s and cortisol were negatively correlated with age; in men, age was negatively correlated with FT3. Although correlation coefficients (r) and significance levels differed between sexes and hormones, DHEA-s concentration was highly correlated with age and declined with age in both men and women. An age-structured model was developed from the regression of mean DHEA-s concentration and median age of each group. The confidence limits for the regression were small and imply that the predictions from the model are accurate.Conclusion: We developed an age-structured model of age related to serum DHEA-s concentration. It may be useful as an index for evaluating the functional age of the endocrine system in Japanese men and women.