Q J Med 2001; 94: 31-37
© 2001 Association of Physicians
Insulin action and insulin secretion in polycystic ovary syndrome treated with ethinyl oestradiol/cyproterone acetate
From the Metabolic Unit, Royal Victoria Hospital, Royal Maternity Hospital and Regional Endocrinology Laboratory, Royal Hospital Trust, Belfast, UK
Received 19 May 2000 and in revised form 20 October 2000
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Summary |
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Polycystic ovary syndrome (PCOS) is associated with abnormalities of insulin action and insulin secretion. Ethinyl oestradiol/cyproterone acetate is a common agent used to treat the symptoms of PCOS, but its effects on insulin action and insulin pulsatility have not been examined. We investigated the relationship between insulin action and insulin secretion in 11 patients with PCOS, at diagnosis and after 3 months of treatment with ethinyl oestradiol/cyproterone acetate, and in 13 controls. Insulin action was assessed using the euglycaemic hyperinsulinaemic clamp (2 mU/kg/min for 2 h). Insulin pulsatility was examined over 90 min by 2 min sampling. Short-term insulin pulses were identified using PULSAR. Treatment with ethinyl oestradiol/cyproterone acetate resulted in significant reductions in testosterone (3.3±0.7 vs. 1.9±0.2 nmol/l, p<0.05), free androgen index (10.2±0.7 vs. 1.2±0.2, p<0.05) and LH/FSH ratio (2.6±0.5 vs. 1.0±0.2, p<0.05). During hyperinsulinaemic clamps, the glucose infusion rate (GIR) required to maintain euglycaemia was lower in PCOS compared to controls (33.6±2.7 vs. 45.1±3.5 µmol/kg/min, p<0.05) but similar in PCOS before and after treatment (33.6±2.8 vs. 33.6±2.7 µmol/kg/min, p=0.9). Numbers of pulses identified in PCOS and controls were similar and unaltered by ethinyl oestradiol/cyproterone acetate. There was no correlation between GIR and frequency of insulin pulses in PCOS before or after treatment (r=0.2, p=0.6; post r=-0.5, p=0.1) unlike controls (r=-0.6, p=0.04). Despite considerable improvement in androgen profile, treatment with ethinyl oestradiol/cyproterone acetate did not alter insulin action in PCOS, and this insulin resistance does not appear to be determined by insulin pulse frequency.
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Introduction |
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Insulin resistance is present in both obese and non-obese women with polycystic ovary syndrome.1–3 In common with other groups at risk of type 2 diabetes mellitus, reduced insulin sensitivity is reflected in higher basal insulin concentrations and diminished insulin-stimulated glucose uptake. Both insulin resistance and disturbances of insulin secretion may contribute to the increased risk of impaired glucose tolerance and type 2 diabetes mellitus associated with polycystic ovary syndrome (PCOS). This risk is considerable, Dunaif1 reporting a 20% prevalence of impaired glucose tolerance or type 2 diabetes mellitus in obese women with PCOS, while Dahlgren3 reported a three-fold increased prevalence of type 2 diabetes mellitus in post-menopausal women with a history of PCOS.
Under normal conditions, insulin is secreted in a pulsatile manner, with both long-term ultradian pulses occurring every 80–150 min and short-term insulin pulses occurring every 8–15 min.4 We have previously reported in normal and diabetic subjects a correlation between the frequency of short-term insulin pulses and peripheral insulin action, with more frequent short-term insulin pulse being present in more insulin-resistant subjects.5 The nature of any relationship between peripheral insulin action and insulin pulse frequency in PCOS is unknown.
Ethinyl oestradiol 35 mcg/cyproterone acetate 2 mg (Dianette, Scherring Health) is commonly used in the UK to treat the clinical manifestations of PCOS. There is very limited information on its effects on insulin action or insulin pulsatility, despite theoretical arguments that this agent may be responsible for either an improvement in insulin action or alternatively for a deterioration in insulin sensitivity.
It has been argued that hyperandrogenism itself is responsible for a state of insulin resistance and hyperinsulinaemia.6–8 Hyperandrogenism is associated with increased abdominal fat deposition, higher concentrations of free fatty acids in the portal circulation and reduced insulin excretion. Testosterone diminishes hepatic insulin clearance and alters muscle fibre composition, producing a greater proportion of fast-twitch fibres, which are less insulin-sensitive. Therefore, any agent which lowers androgen concentrations may potentially improve insulin sensitivity. Others would argue for an alternative pathological sequence in PCOS, with hyperinsulinaemia playing a central role via a stimulatory effect on ovarian P450c promoting ovarian androgen production.9 If this is the true nature of the relationship linking androgens and insulin in PCOS, control of hyperandrogenism would not be expected to alter insulin action. Alternatively, ethinyl oestradiol/cyproterone acetate could be associated with reduced insulin sensitivity and deteriorating glucose tolerance, as reported in healthy women using the oral contraceptive pill.10
The aims of this study were to establish the effect of 3 months of ethinyl oestradiol/cyproterone acetate therapy on insulin action in PCOS, and the nature of the relationship between insulin action and insulin pulsatility in PCOS before and after treatment.
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Methods |
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Patients
Eleven patients with PCOS were recruited from the endocrine and gynaecology clinics of the Royal Victoria Hospital, Belfast. Hirsutism, amenorrhoea or oligomenorrhoea, hyperandrogenism and typical ovarian appearances on abdominal or vaginal ultrasound were all required to establish a diagnosis of PCOS. All ultrasound scans were performed by one observer (AIT)—a consultant gynaecological endocrinologist. Subjects whose weight exceeded 125% of ideal body weight (Metropolitian Life Insurance Tables 1955) were excluded.
Thirteen controls were recruited from hospital staff. All controls had normal androgen levels, regular menstrual cycles and no evidence of hirsutism. No patient or control was taking any medication known to affect insulin action or insulin secretion in the 3-month period prior to recruitment. All subjects gave written informed consent and the protocol was approved by the Ethics Committee of the Queen's University of Belfast.
Design
Assessments of insulin action and insulin pulsatility were made within 1 week of each other. Controls had these assessments carried out during the follicular phase of the menstrual cycle. PCOS subjects had assessment of insulin action and insulin pulsatility at baseline and after 3 months of ethinyl oestradiol/cyproterone acetate therapy. Initial assessment was performed during a period of amenorrhoea or during the follicular phase of the menstrual cycle (confirmed by progesterone level) and the second assessment during a withdrawal bleed which followed the third cycle of ethinyl oestradiol/cyproterone acetate.
Assessment of insulin action
Insulin action was assessed using the euglycaemic hyperinsulinaemic clamp technique. Patients were admitted at 0745 h on the morning of the study after a 12 h overnight fast. An antecubital vein was cannulated (18 gauge, Venflon Viggo) and was used for all infusions. A further cannula (18 gauge) was inserted retrogradely into a dorsal hand vein on the opposite arm, and the hand placed in a temperature-controlled plexiglass box (Northern Ireland Technology Centre, Automated Division, Queen's University of Belfast) maintained at 55°C to allow intermittent sampling of arterialized venous blood. A primed continuous infusion of HPLC-purified [3-3H]glucose (Du Pont-NEN) (net 100 c) was given during an equilibrium period (–120 min to time 0). The priming dose of [3-3H]glucose was adjusted according to the fasting plasma glucose.11 After an equilibration period, a 2 h continuous infusion of insulin (Humulin S, Lily) was commenced at 2 mU/kg/min. Plasma glucose was maintained at the fasting concentration by an exogenous glucose infusion (20%). Exogenous glucose was prelabelled with [3-3H]glucose to match the predicted basal glucose activity as described previously with the modification that the primed continuous tracer infusion was reduced to 50% of basal at 20 min and 25% of basal at 40 min (to maintain tracer steady state) and was maintained at this rate throughout the remainder of the hyperinsulinaemic period.11,12
Determination of glucose turnover
Plasma for measurement of glucose specific activity was deproteinized with barium hydroxide and zinc sulphate. After centrifugation, the supernatant was counted in a liquid scintillation spectrometer (Tn-Carb 2000 CA, Canberra Packard). Aliquots of tracer infusate and labelled exogenous glucose infusion were spiked into nonradioactive plasma and processed in parallel with plasma samples to allow calculation of [3-3H]glucose infusion rates.
The non-steady-state equations of Steele,13 as modified by De Bodo,14 were used to determine rates of glucose appearance and disappearance at time -30 to 0 min and 90–120 min, assuming a pool fraction of 0.65 and an extracellular volume of 190 ml/kg. Infusion rates of [3-3H]glucose were calculated as sums of the tracer infused continuously and the tracer in the labelled exogenous glucose infusion. Rates of endogenous (hepatic) glucose production were calculated by subtraction of the exogenous glucose rates required to maintain euglycaemia from the isotopically determined rates of glucose appearance.
Assessment of insulin pulsatility
Subjects were admitted on a separate occasion at 0830 h after a 12 h overnight fast. A cannula (21 gauge, Venflon Viggo) was inserted into a large antecubital vein and the arm placed in a temperature-controlled box maintained at 55°C as described above. After a 30 min rest period, blood was withdrawn every 2 min for 90 min for determination of insulin concentrations. Insulin pulses were subsequently identified using the peak detector algorithm PULSAR.5,15,16 This computer program identifies pulses in terms of height and duration above a smooth baseline using the coefficient of variation (CV) as a scaling factor. Values of total insulin area above the smoothed baseline are also available with this program. We have used this latter value as a measure of total pulse-related insulin area.
Hormone measurement
Serum insulin was measured by enzyme-linked immunoabsorbent assay (Abbot IMx, Abbott Laboratories). This assay does not display cross-reactivity with proinsulin or split products. The intra-assay CV in our laboratory during the study was 2.5% at a mean insulin concentration of 5.2 mU/l. Follicular stimulating hormone (FSH), luteinizing hormone (LH) and sex-hormone-binding globulin (SHBG) were analysed by two-site fluoroimmunometric assay (Auto DELFIA, Purkin). Testosterone was measured by radioimmunoassay (Diagnostic Products).
Statistical analysis
All data are expressed as means±SEM. Differences between PCOS subjects and controls were analysed using unpaired Student's t-test. Differences in PCOS subjects before and after ethinyl oestradiol/ cyproterone acetate treatment were analysed by the paired Student's t-test. Associations between variables were assessed by Spearman rank correlation. Statistical significance was taken at the p=0.05 level.
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Results |
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There were no significant differences in age, BMI, fasting glucose, HbA1c or total cholesterol between PCOS subjects and controls (Table 1
). Treatment with ethinyl oestradiol/cyproterone acetate did not change any of these variables.
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Before treatment, PCOS subjects (Table 2
had higher concentrations of testosterone and lower concentrations of sex-hormone-binding globulin (SHBG) than controls leading to a raised free androgen index (FAI). LH/FSH ratio was higher in PCOS subjects. Treatment with ethinyl oestradiol/cyproterone acetate resulted in a significant decrease in testosterone, an increase in SHBG and normalization of FAI and LH/FSH ratios.
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The results from the glucose clamp studies are shown in Figure 1
. Glucose and insulin concentrations in the fasting state and during the clamp were similar for PCOS subjects and controls and did not change after ethinyl oestradiol/cyproterone acetate. The glucose infusion rate (GIR) required to maintain euglycaemia was significantly lower in the PCOS group compared with controls (33.6±2.8 vs. 45.1±3.5 µmol/kg/min). Treatment with ethinyl oestradiol/cyproterone acetate did not alter insulin action as expressed by GIR.
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Post-absorptive endogenous glucose production was similar in PCOS subjects before and after treatment with ethinyl oestradiol/cyproterone acetate (12.4±1.7 vs. 11.5±0.6 µmol/kg/min). Endogenous glucose production was suppressed to a comparable extent during the 2 mU/kg/min insulin infusion in PCOS before and after therapy (5.3±0.7 vs. 5.9±1.3 µmol/kg/min, p=0.6). Post-absorptive endogenous glucose production in controls was similar to PCOS subjects (12.7±0.6 vs. 12.4±1.7 µmol/kg/min, p=0.8) and suppressed to a similar extent in response to the 2 mU/kg/min insulin infusion (6.6±0.6 vs. 5.3±0.7 µmol/kg/min, p=0.1).
The results of the insulin pulse analysis are shown in Table 3. Similar numbers of pulses were identified in controls and PCOS subjects before treatment. Ethinyl oestradiol/cyproterone acetate did not alter pulse frequency in PCOS subjects. Total insulin area and pulse-related insulin area tended to be higher for PCOS subjects compared with controls, and also higher in PCOS after treatment compared to before treatment with ethinyl oestradiol/cyproterone acetate, but neither of these differences reached statistical significance.
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Correlations of insulin sensitivity and measures of insulin secretion are shown in Table 4
. There was a significant negative correlation between frequency of insulin pulses and GIR (r=-0.6, p=0.04) in controls, but this relationship was not present in PCOS before or after ethinyl oestradiol/cyproterone acetate.
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The most insulin-resistant PCOS subjects tended to have higher total insulin areas (r=-0.74, p=0.02) and total pulse-related insulin areas (r=-0.7, p=0.01) before treatment, but after ethinyl oestradiol/cyproterone acetate therapy this trend disappeared. No such correlations were present in controls.
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Discussion |
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Polycystic ovary syndrome, although a common disorder, remains poorly understood. Much debate continues regarding its pathogenesis and as yet no universally accepted diagnostic criteria have been identified. Insulin resistance is an important feature of this condition. Previously it was felt that insulin resistance in PCOS was not associated with the other features of the Insulin Resistance Syndrome (Syndrome X—dyslipidaemia, hypertension, premature atherosclerosis and increased risk of type 2 diabetes mellitus).17 Accumulating evidence now suggests that these women do have an excess risk not only of impaired glucose tolerance and type 2 diabetes, but also of hypertension and dyslipidaemia.1,2,18–20 It is therefore imperative that therapeutic interventions designed to control symptoms of PCOS do not increase the risk of these disorders by further reducing insulin sensitivity in an already insulin-resistant population. Ethinyl oestradiol in combination with cyproterone acetate (Dianette) is the agent most commonly used in the UK to treat manifestations of PCOS, such as hirsutism, but its effect on insulin resistance, using gold-standard glucose-clamp methodology, has not been previously examined.
We used strict diagnostic criteria to define a PCOS group. As expected, this study group were significantly more insulin-resistant than controls. Treatment with ethinyl oestrdiol/cyproterone acetate proved very effective in reducing androgen levels during the 3-month study period compared with baseline. This is in concordance with previous reports suggesting that ethinyl oestradiol/cyproterone acetate reaches maximal biochemical effectiveness by the third month of treatment.21
The suggestion that hyperandrogenism itself contributes to the pathogenesis of insulin resistance associated with PCOS has stimulated interest in the effects of androgen-lowering treatment modalities on insulin sensitivity. Treatment with gonadotrophin releasing hormone (GnRH) agonists are highly effective in reducing hyperandrogenism, but have largely been disappointing in their effects on insulin sensitivity. Dunaif22 reported no change in insulin-mediated glucose disposal, insulin concentrations or hepatic glucose production in PCOS subjects treated for 12 weeks with superagonist GnRH analog. Lasco23 reported similar results after 5 months treatment with leuprolide. Both these studies used the glucose clamp technique and included obese PCOS subjects. Moghetti24 reported an improvement in both oxidative and nonoxidative glucose metabolism in hyperandrogenic women treated with the anti-androgen agent flutamide, the GnRH agonist buserelin and spironolactone. This improvement in insulin action was noted in obese subjects. Our current study demonstrates that in a clearly defined PCOS group, significant reductions in testosterone levels were not associated with any improvement in insulin action.
We accept that this study does not allow separate analysis of the possible effects of the components of Dianette, but it is reassuring that this oestrogen/progestogen combination did not result in any deterioration in insulin action. Information regarding treatment with the oral contraceptive pill or Dianette in PCOS remains limited. Korykowski,25 using the hyperglycaemic clamp, demonstrated reduced insulin sensitivity index after 3 months of treatment with a low-dose triphasic oral contraceptive. Seed et al.,26 using fasting glucose and insulin levels, demonstrated increased insulin resistance after 12 weeks of treatment with ethinyl oestradiol/cyproterone acetate. Weight loss and increased physical training remain the only interventions which have consistently associated with improvements in insulin action in PCOS.27–30
With insulin infusions designed to mimic basal or mean basal concentrations, pulsatile insulin results in greater lowering of blood glucose and suppression of glucose production than continuous delivery.31,32 A negative correlation between basal insulin pulse frequency and glucose uptake at higher physiological concentrations has been reported in normal subjects16 and in type 2 diabetes.5 It has been suggested that continued exposure to asynchronous insulin pulses may induce receptor or post-receptor defects. Short-term insulin pulses are more frequent and irregular in type 2 diabetes mellitus, and could represent an important early abnormality in the pathogenesis of insulin resistance in this condition.33 In the present study, we confirm the negative correlation between pulse frequency and peripheral glucose uptake in control subjects. However this relationship was not present in PCOS either before or after treatment. While it is possible that with larger numbers of patients a relationship may emerge, it may well be that insulin resistance in PCOS arises from different pathogenic mechanisms from those in type 2 diabetes mellitus.
We conclude that reduction of androgens did not improve insulin action and that androgens are not involved in maintaining insulin resistance in PCOS once it has been established. Furthermore, insulin resistance in PCOS was not determined by insulin pulse frequency.
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Acknowledgments |
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During the course of this study, VLA and MIW were in receipt of Royal Victoria Hospital Research Fellowships. We thank Sister R. Humphries and the nursing staff of the Metabolic Unit for assistance during clinical studies. Mrs Marie Loughran and Miss Mabel Hazlett provided excellent secretarial help. We are also grateful to Dr C. Patterson, Department of Community Medicine and Medical Statistics, The Queen's University of Belfast, for statistical advice.
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Notes |
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Address correspondence to Dr P.M. Bell, Royal Victoria Hospital, Grosvenor Road, Belfast BT12 6BA
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References |
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1. Dunaif A, Graf M, Modeli J, Laumas V, Dobransky A. Characterisation of groups of hyperandrogenic women with acanthosis nigricans, impaired glucose tolerance and or hyperinsulinaemia. J Clin Endocrinol Metab1987; 65:499–507.[Abstract]
2. Dunaif A, Segal KR, Futterweit W, Dobransky A. Profound peripheral insulin resistance independent of obesity in polycystic ovary syndrome. Diabetes1989; 38:1165–74.[Abstract]
3. Dahlgren E, Johansson S, Lindstedt G, Knutsson F, Oden A, Janson P-O, Mattson LA, Crona N, Lundberg P-A. Women with polycystic ovary syndrome with wedge resection in 1956–1965: A long term follow up focusing on natural history and circulating hormones. Fertil Steril1992; 57:505–13.[ISI][Medline]
4. Lang DA, Mathews DR, Peto J, Turner RC. Cyclic oscillations of basal plasma glucose and insulin concentrations in human beings. N Engl J Med1979; 301:1023–7.[Abstract]
5. Hunter SJ, Atkinson AB, Ennis CN, Sheridan B, Bell PM. Associations between insulin secretory pulse frequency and peripheral insulin action in NIDDM and normal subjects. Diabetes1996; 45:683–6.[Abstract]
6. Shoupe D, Lobo RA. The influence of androgens on insulin resistance. Fertil Steril1984; 41:385–8.[ISI][Medline]
7. Nader S. Polycystic ovary syndrome and the androgen insulin connection. Am J Obstet Gynecol1991; 165:346–8.[ISI][Medline]
8. Polderman KH, Gooren LJG, Asscheman H, Bakker A, Heine RJ. Induction of insulin resistance by androgens and oestrogens. J Clin Endocrinol Metab1994; 79:265–71.[Abstract]
9.
Nestler JE, Jakubowicz DJ. Decrease in ovarian cytochrome P450c 17 activity and serum free testosterone after reduction of insulin secretion in polycystic ovary syndrome. N Engl J Med1996; 335:617–23.
10. Godsland IF, Walton C, Felton C, Proudler A, Patel A, Wynn V. Insulin resistance, secretion and metabolism in users of oral contraceptives. J Clin Endocrinol Metab1992; 74: 64–70.[Abstract]
11. Harper R, Ennis CN, Heaney AP, Sheridan B, Gormley M, Atkinson AB, Johnston GD, Bell PM. A comparison of the effects of low and conventional dose thiazide diuretics on insulin action in hypertensive patients with non-insulin-dependent diabetes. Diabetologia1995; 38:853–9.[ISI][Medline]
12. Neely RDG, Rooney DP, Bell PM, Bell NP, Sheridan B, Atkinson AB, Trimble EM. Influence of growth hormone on glucose-6-phosphate cycle and insulin action in normal humans. Am J Physiol1992; 264:E980–7.
13.
Steele R, Walls JS, De Bodo RC, Altszuler N. Measurement of size and turnover rate of body glucose pool by the isotope dilution method. Am J Physiol1956; 187:15–25.
14. De Bodo RC, Steele R, Altszuler N, Dunn A, Bishop JS. The hormone regulation of carbohydrate metabolism: studies with C14 glucose. Recent Prog Horm Res1963; 19:445–88.
15.
Merriam GR, Wachter KW. Algorithms for the study of episodic hormone secretion. Am J Physiol1982; 243:E310–18.
16. Peiris AN, Stagner JI, Vogel RL, Nakagawa A, Samols E. Body fat distribution and peripheral insulin sensitivity in healthy men: role of insulin pulsatility. J Clin Endocrinol Metab1992; 75:290–4.[Abstract]
17. De Fronzo RA, Ferrannini E. Insulin Resistance; A multifaceted syndrome responsible for NIDDM, obesity, hypertension, dyslipidaemia and atherosclerotic cardiovascular disease. Diabetes Care1992; 75:508–13.
18. Wild RA, Pointer PC, Carlson PB, Carruth LB, Ramey GB. Lipoprotein lipid concentrations and cardiovascular risk in women with polycystic ovary syndrome. J Clin Endocrinol Metab1985; 61:945–51.
19. Wild RA. Obesity, lipids, cardiovascular risk and androgen excess. Am J Med1995; 98:S27–32.[Medline]
20. Graf M, Brown V, Richards C, Meissner L, Dunaif A. The independent effects of hyperandrogenaemia, hyperinsulinaemia and obesity in lipid and lipoprotein profiles in women. Clin Endocrinol1990; 33:119–31.[Medline]
21. Golland IM, Elstein ME. Results of a one year open study with Diane-35 in women with polycystic ovary syndrome. Ann NY Acad Sci1993; 687:263–71.[Abstract]
22. Dunaif A, Green G, Futterweit W, Dobransky A. Suppression of hyperandrogenism does not improve peripheral or hepatic insulin resistance in polycystic ovary syndrome. J Clin Endocrinol Metab1990; 70:699–704.[Abstract]
23. Lasco A, Cucinotta D, Gigante A, Denuzzo G, Pedulla M, Trifiletti A, Frisina N. No change of peripheral insulin resistance in polycystic ovary syndrome after reduction of endogenous androgens by leuprolide. Eur J Endocrinol1995; 133:718–22.[Abstract]
24. Moghetti P, Tosi F, Castello R, Magnani CM, Negri C, Brun E, Furlani L, Caputo M, Muggeo M. The insulin resistance in women with hyperandrogenism is partially reversed by antiandrogen treatment: Evidence that androgens impair insulin action women. J Clin Endocrinol Metab1996; 81:953–60.
25. Korykowski MT, Mokan M, Horwitz MJ, Berga SL. Metabolic effects of oral contraceptives in women with polycystic ovary syndrome. J Clin Endocrinol Metab1995; 80:3327–34.[Abstract]
26. Seed M, Godsland V, Wynn V, Jacobs HS. The effects of cyproterone acetate and ethinyl oestradiol on carbohydrate metabolism. Clin Endocrinol1984; 21:689–99.[Medline]
27. Jaatinen T-A, Laippala P, Anttila L, Ruutiainen K, Erkkola R, Scheinin M, Koskinen P, Irjala K. Hormonal responses to physical exercise in patients with polycystic ovarian syndrome. Fertil Steril1993; 60:262–7.[ISI][Medline]
28. Kiddy DS, Hamilton-Fairley D, Bush A, Short F, Anyaoku V, Reed MJ, Franks S. Improvement in endocrine and ovarian function during dietary treatment of obese women with polycystic ovary syndrome. Clin Endocrinol1992; 36:105–11.[Medline]
29. Holte J, Bergh T, Berne C, Wide L, Lithell H. Restored insulin sensitivity but persistently increased early insulin secretion after weight loss in obese women with polycystic ovary syndrome. J Clin Endocrinol Metab1995; 80:2586–93.[Abstract]
30. Andersen P, Seljeflot I, Abdelnoor M, Arnesen H, Dale PO, Lovik A, Birkeland K. Increased insulin sensitivity and fibrinolytic capacity after dietary intervention in obese women with polycystic ovary syndrome. Metabolism1995; 44:611–16.[ISI][Medline]
31. Mathews DR, Naylor BA, Jones RG, Ward GM, Turner RC. Pulsatile insulin has a greater hypoglycaemic effect than continuous delivery. Diabetes1983; 32:617–21.[Abstract]
32. Paolisso G, Scheen AJ, Giugliano D, Sgambato SE, Albert A, Varrichio M, D'Onofrio F, Lefebvre PJ. Pulsatile insulin delivery has greater metabolic effects than continuous hormone administration in man: Importance of pulse frequency. J Clin Endocrinol Metab1991; 72:607–15.[Abstract]
33. O'Rahilly S, Turner RC, Mathews DR. Impaired pulsatile secretion of insulin in relatives of patients with non-insulin-dependent diabetes. N Engl J Med1988; 318:1225–30.[Abstract]
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