[1] Harvard Univ, Sch Publ Hlth, Program Populat Genet, Boston, MA 02115 USA
[2] Beijing Univ, Affiliated Hosp 3, Div Endocrinol, Beijing, Peoples R China
[3] Beijing Univ, Ctr Ecogenet & Reprod Hlth, Beijing, Peoples R China
[4] Beijing Univ, Affiliated Hosp 1, Div Endocrinol, Beijing, Peoples R China