Serum soluble transferrin receptor (sTfR) concentrations and sTfR/ferritin ratio in premenopausal women: associations with glucose tolerance, insulin sensitivity and androgen excess
Héctor F Escobar-Morreale1 & Manuel Luque-Ramírez1,2
Context: Androgen excess may contribute to the increased body iron stores of polycystic ovary syndrome (PCOS) by stimulating erythropoietic activity.
Objective: To estimate iron stores and erythropoietic activity in premenopausal women, considering simultaneously the effects of PCOS, obesity and abnormal glucose tolerance.
Design: Casecontrol study.
Settings: Academic hospital.
Patients: One-hundred four PCOS patients and 100 non-hyperandrogenic women.
Interventions: Basal blood sampling and oral glucose tolerance test.
Main outcome measures: Serum soluble transferrin receptor (sTfR) and ferritin concentrations, and indexes of inflammation, obesity, and insulin and glucose metabolism.
Results: Ferritin levels increased in women presenting with PCOS, obesity, and/or abnormal glucose tolerance, but these disorders did not influence sTfR concentrations. The sTfR/ferritin ratio decreased with obesity and abnormal glucose tolerance and its logarithm correlated inversely with BMI, free testosterone and C-reactive protein levels, and directly with the insulin sensitivity and disposition indexes. Moreover, a stepwise multiple regression analysis indicated the changes in the insulin sensitivity and disposition indexes, and not those in other variables, explained 9% of the variability of the logarithm of sTfR/ferritin ratio.
Conclusions: Enhancement of erythropoiesis by androgen excess does not explain the finding of increased ferritin levels in PCOS patients, yet reduced insulin sensitivity and disposition increased ferritin levels in premenopausal women. However, the lack of changes in sTfR with PCOS, obesity and abnormal glucose tolerance suggests that the increased ferritin levels associated with these conditions indicate not only augmented body iron stores, but also the role of ferritin as an inflammatory marker.
Grants: FIS PI080944, CIBERDEM CB07/08/0005.