Endocrine Abstracts (2002) 3 P103

The utility of the HOMA model for identifying women with polycystic ovarian syndrome (PCOS) who are insulin resistant

AH Heald1, S Whitehead1, S Anderson1, I Laing2 & H Buckler1

1Department of Endocrinology, University of Manchester, Salford NHS Trust, Salford, UK; 2Clinical Biochemistry Department, Manchester Royal Infirmary, Manchester, UK.

OBJECTIVE Recent studies have shown the benefits of insulin sensitising agents such as Metformin in the treatment of infertility and hirsuitism in PCOS. However not all women with PCOS are insulin resistant. Within a clinic population of women referred for treatment of hirsuitism, we examined the utility of fasting insulin/glucose measurement in identifying which women were insulin resistant.

DESIGN We evaluated an outpatient clinic group of 25 PCOS patients all referred for treatment of hirsuitism and a matched community control group of 25 BMI matched healthy non-PCOS women. All underwent a 75g oral glucose tolerance test (OGTT) with insulin measurement. Insulin sensitivity was calculated using the HOMA-model which correlates strongly with direct measurements of insulin sensitivity.

RESULTS Using a HOMA-S (insulin sensitivity) cut-off value of 0.4, insulin resistance was found in 16/25 women. HOMA-S correlated strongly negatively with area under the curve (AUC) insulin (rho=-0.56, p=0.01) and peak insulin (rho=-0.59), p=0.01). Of the 25 patients, 1 had diabetes, 3 had impaired glucose tolerance and 1 impaired fasting glucose (WHO criteria, 2001). BMI for the PCOS women was 32.7 (95% CI 29.9-35.9).

Fasting insulin was significantly higher in the PCOS women at 15.0 (11.1-18.8) mU/l vs controls 6.9 (5.9-8.0) mu/l, (F=10.1, p<0.001); as was 2hr insulin 57.7 (37.7-77.7) mu/l vs 35.4 (28.3-44.4) mu/l, (F=12.2, p<0.001). HOMA-S was corresponding lower for the PCOS women (0.36 [0.15-0.55]) than controls (0.87 [0.70-1.03]), (F=6.3, p=0.01) with HOMA-B (pancreatic beta-cell function) being correspondingly higher at 274 (219-328) for PCOS women vs 105 (70-139) for controls, (F=26.3, p<0.001).

CONCLUSION Despite their high BMI, only two thirds of PCOS women studied were insulin resistant. The question remains as to whether insulin resistance in PCOS women is a predictor of response to Metformin treatment. Routine HOMA-S measurement may significantly add to the understanding of benefits of Metformin in this group.Insulin sensitising agents are increasingly being used in the treatment of PCOS. We feel that some index of insulin sensitivity prior to commencement on treatment is needed and that our data makes a strong case for the use of HOMA-S

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