A TWIN STUDY OF POLYCYSTIC-OVARY-SYNDROME AND LIPIDS

Our objective was to assess the relative contribution of genetic and e nvironmental factors (particularly androgens) on circulating levels of lipid fractions and to determine the effect, if any, of polycystic ov ary syndrome (PCOS) on lipid fractions. The study was carried out in t he outpatient clinic of the Royal Hospital for Women, Paddington, Sydn ey, Australia. A group of 19 monozygotic (MZ) and 15 dizygotic (DZ) tw in pairs was identified from the National Twin Register. Ultrasound cl inical and biochemical parameters were used to define polycystic ovari es. Serum androgen and lipid fractions were also measured. Eleven pair s of twins (five MZ, six DZ) were scan discordant (i.e. one twin had p olycystic ovaries and the co-twin did not). Serum levels of the lipopr otein fraction in twins with polycystic ovaries were not significantly different from the levels found for their co-twins with normal ovarie s. There were no significant correlations between androgen-related hor mones and any of the lipid measurements. Body mass index (BMI) was pos itively correlated with triglycerides and lipoprotein (a), and negativ ely correlated with high-density lipoprotein cholesterol (HDL-C). Sex hormone-binding globulin (SHBG) levels were negatively correlated with triglycerides and lipoprotein (a) and positively associated with HDL- C. Fasting insulin levels were significantly correlated with triglycer ides and negatively with HDL-C. The MZ intraclass correlation exceeded that of the DZ twin pairs for all the lipid variables measured. The h eritability estimates for lipoprotein (a), apolipoprotein B, total cho lesterol and HDL-C were 0.95, 0.56, 0.48 and 0.54, respectively. Howev er, the intraclass correlation coefficient for triglycerides was not s ignificantly different between MZ and DZ twins, but maximum likelihood analysis indicated that at least 10% of the variance of the circulati ng triglyceride concentration is determined by genetic factors. We con clude that twins discordant for the PCOS do nor have significantly dif ferent lipid fractions.