Carbohydrate and lipid metabolic studies before and after one year of treatment with ethynodiol diacetate in "normal" women

Androgenicity of progestins in hormonal contraceptives and the risk of gestational diabetes mellitus

OBJECTIVE

There is some evidence that use of hormonal contraceptives, particularly the more androgenic formulations, can alter a woman's glucose tolerance. We examined the association between hormonal contraceptive use, categorized by the androgenicity of the progestin component, and risk of gestational diabetes mellitus (GDM) in a nested case-control study.

RESEARCH DESIGN AND METHODS

Case (n = 356) and control (n = 368) subjects were selected from a multiethnic cohort of 14,235 women who delivered a singleton live birth between 1 January 1996 and 30 June 1998, who were screened for GDM at 24-28 gestational weeks, and who were members of Kaiser Permanente for at least 5 years before pregnancy. GDM was defined using the National Diabetes Data Group plasma glucose cutoffs. Information concerning hormonal contraceptive use during the 5 years before pregnancy was obtained from medical charts and some pharmacy data.

RESULTS

There was a suggestion that compared with no hormonal contraceptive use, use of a low-androgen hormonal contraceptive before pregnancy was associated with a slight reduction in risk of GDM (odds ratio 0.84 [95% CI 0.58-1.22]), whereas use of a high-androgen hormonal contraceptive was associated with a modest increase in GDM risk (1.43 [0.92-2.22]).

CONCLUSIONS

The effects of hormonal contraceptive use on GDM risk may vary by the androgenicity of the progestin component.

Effects of oral contraceptives on glucose flux and substrate oxidation rates during rest and exercise

We examined the effects of oral contraceptives (OC) on glucose flux and whole body substrate oxidation rates during rest (90 min) and two exercise intensities [60-min leg ergometer cycling at 45 and 65% peak O(2) uptake (Vo(2 peak))]. Eight healthy, eumenorrheic women were studied during the follicular and luteal phases before OC and the inactive and high-dose phases after 4 mo of a low-dose, triphasic OC. Subjects were studied in the morning 3 h after a standardized (308 kcal) breakfast. There were significant reductions in glucose rates of appearance and disappearance during exercise of both intensities with OC but not rest. There were no phase effects on substrate oxidation during rest or exercise. These results are interpreted to mean that, in women fed several hours before study, 1) OC decreases glucose flux, but not overall carbohydrate and lipid oxidation rates during moderate-intensity exercise; and 2) synthetic ovarian hormone analogs in the doses contained in OC have greater metabolic effects on glucose metabolism during exercise than do endogenous ovarian hormones.

Carbohydrate metabolism before and after Norplant removal

Changes in carbohydrate metabolism, measured by oral glucose tolerance test, were studied in Norplant users before and after removal. The mean area under the glucose curve rose from 24.7 min mmol/L before Norplant insertion to 35.1 min mmol/L before removal and decreased to 26.1 min mmol/L four weeks after Norplant removal. The areas before insertion and after removal were not statistically different (95% confidence interval -3.3 to 0.56, P = 0.16). The mean areas under the insulin curves before insertion (53.14 min uU/L) and after removal (59.46 min uU/L), however, were significantly different (95% confidence interval -7.64 to -5.0, P less than 0.0001). We conclude that changes in carbohydrate metabolism induced by Norplant are reversible once the implants are removed. While the changes in glucose induced by Norplant returned to pre-insertion levels within 4 weeks after removal, insulin changes were slower to return to pre-insertion values.

The effect of continuous subdermal levonorgestrel (Norplant) on carbohydrate metabolism

Blood glucose and plasma insulin levels during an oral glucose tolerance test were measured in 20 women using continuous subdermal levonorgestrel (Norplant) for contraception over a 12-month period. Changes in carbohydrate metabolism occurred as early as 1 month but were most marked after 6 months. After 1 month the area under the glucose and insulin curves increased by 12.3% and 37.7%, respectively. This increase was more marked by 6 months, but by 12 months it was significantly less marked. Although changes in the blood glucose and plasma insulin levels at different times during the oral glucose tolerance test occurred, they were all within normal limits for normal women. The peak blood glucose and insulin levels after insertion of the implant occurred 60 minutes after the glucose load, as opposed to 30 minutes before insertion. Apart from this, there was a significant delay in the return of these levels to fasting values. We conclude that this product, like any other progesterone-containing contraceptive, alters carbohydrate metabolism, but these alterations are not clinically significant in normal women. It is, however, possible that in potential cases of diabetes it may predispose to frank diabetes.

Changes in carbohydrate metabolism during 30 months on Norplant

During a 30-month period, changes in carbohydrate metabolism (measured by oral glucose tolerance test) were studied in 20 Norplant acceptors. Changes were first observed one month after Norplant insertion and peaked between 12-18 months. The area under the glucose curve rose by 12.3% and 40.5% one and 12 months post insertion, respectively. At 18, 24 and 30 months the rise was, respectively, 41.9%, 40% and 38.6%. Although the changes under the insulin curves were similar, the increase at one month was doubled (25.7%). Only fasting insulin values showed very slight and insignificant changes during the 30-month period. All the changes were, however, within the normal limits for healthy women. We conclude that although Norplant induces changes in carbohydrate metabolism, these changes remain within normal limits, peak at 12 months and either remain the same or decrease with time.

Clinical aspects of the relationship between oral contraceptives, abnormalities in carbohydrate metabolism, and the development of cardiovascular disease

Although large epidemiologic studies indicated no difference in the frequency of diabetes mellitus in nonusers and everusers of high-dose combination oral contraceptives, other studies had shown an increased risk of impaired glucose tolerance in current users, which is estimated to be roughly twice as frequent as that in nonusers. Women at risk of developing impaired glucose tolerance while receiving high-dose oral contraceptives either had previous gestational diabetes mellitus or were older, obese, or had a positive family history of diabetes mellitus. The tendency to decreased glucose tolerance seems essentially related to the dosage and chemical structure of the progestogen used in oral contraceptives, namely, estrane and particularly gonane progestins. However, increased frequency of impaired glucose tolerance and potentially diabetes mellitus are obviously not linked to the use of the more potent gonane progestins. The use of low-dose oral contraceptives, particularly with reduced progestogen content (such as in the triphasic formulations and last-generation monophasic preparations), is accompanied by a low risk of impaired glucose tolerance, even in previous gestational diabetes mellitus. The mechanism of decreased glucose tolerance in oral contraceptive users is unknown but seems related partially to increased peripheral resistance that is potentially caused by a postreceptor defect in insulin action. Changes in insulin production or metabolic clearance rate are not excluded by recent, sophisticated investigations of carbohydrate metabolism in oral contraceptive users. Impaired glucose tolerance and diabetes mellitus, chronic hyperglycemia, and hyperinsulinemia are believed to increase atherogenic risk either by their direct action or their effects on lipid metabolism. Newer epidemiologic studies now indicate that the incidence of cardiovascular disease in low-dose, low-risk, current oral contraceptive users has been substantially decreased. The use of low-dose oral contraceptives with reduced dosages of better adapted progestogens seems effective in decreasing alterations in carbohydrate metabolism and may thereby contribute to decrease further atherogenic risk in oral contraceptive users.

Mechanism of action of oral contraceptives on carbohydrate metabolism at the cellular level

Although the available scientific data on the undesired metabolic effects of sex steroids have accumulated rapidly, most are of a descriptive nature, and only a few studies elucidate the impact at the cellular level and the possible interrelationship between different metabolic systems. This review summarizes the influence of different contraceptive steroid combinations on glucose metabolism and points to the possible mechanisms behind a disturbance of the euglycemic homeostasis with a concomitant change in lipid metabolism. Today the general concept is that the influence of combined sex steroid products on glucose metabolism is mainly caused by the progestogen components, although artificial estrogens may act synergistically. The diabetogenic effects of the progestogens make it important to consider the development during the last decade of the new more selective progestogens of the gonane type. From recent studies it seems, however, that intake of contraceptive combinations of ethinyl estradiol in combination with these types of gonanes, such as desogestrel and gestodene, may also be accompanied by increased insulin resistance, specifically, a hyperinsulinemic response to a glucose challenge despite unchanged glucose values compared with a baseline test. This is similar to observations made with combinations of ethinyl estradiol and other more traditional types of progestogens of the gonane and estrane type. It is conceivable that the diabetogenic effects of the progestogens are caused by a change in insulin receptor binding or a postreceptor defect in the cellular insulin action. The clinical implications of the diabetogenic effects of the sex steroids are hard to interpret, but more long-term exposure of arterial tissue to elevated concentrations of glucose and insulin results in inhibition of lipolysis and synthesis of cholesterol and triglycerides, which result in the development of lipid-filled lesions--fatty streaks--similar to those of early atherosclerosis.

Alterations in carbohydrate metabolism as they apply to reproductive endocrinology

This review has characterized the current state of knowledge of four clinical situations in which an interrelationship of gynecology, endocrinology and carbohydrate metabolism is recognized. The literature contains conflicting descriptions of changes in glucose homeostasis during the menstrual cycle and while using birth control pills. Physiologic changes in receptor number have been demonstrated in each of these situations, so failure to observe differences using glucose tolerance testing may reflect an in vivo homeostatic response to changes in these hormone levels. Thus, in vivo identification of alterations in carbohydrate metabolism induced by endogenous or exogenous steroids may require utilization of models that prevent these homeostatic mechanisms. The association between hyperandrogenism and hyperinsulinism has been better characterized, but the relationship is complicated by the frequent coexistence of obesity. The association may be due to insulin-stimulated ovarian androgen production, and insulin insensitivity may reflect a postreceptor defect. Insulin and its metabolic effects have also been implicated in ovulatory dysfunction in women with diabetes mellitus and identified as a factor affecting all levels of the hypothalamic-pituitary-ovarian axis. A clearer understanding of these relationships and their application to clinical management await further study.

Metabolic effects of oral contraceptives

Combination oral contraceptives (OCs) are probably not an independent risk factor for cardiovascular disease but through their metabolic actions, may partly amplify the effects of known risk factors for cardiovascular disease. This review of the literature and our own data indicate that use of high-dose, progestogen-dominant OCs induces a potentially atherogenic lipoprotein profile (high low-density lipoprotein-cholesterol:high-density lipoprotein-cholesterol ratio), mostly attributable to the antiestrogenic action of the progestogen content of these OCs. In contrast, lower-dose combination OCs with reduced amounts of progestogens and slight estrogen dominance, either monophasic or multiphasic, produce strikingly fewer adverse effects on lipoproteins. Moreover, use of low-dose, as opposed to high-dose, OCs results in almost unchanged glucose tolerance, marginally increased or unchanged insulin and glucagon responses to glucose, and probably unchanged levels and activity of peripheral insulin receptors. Further in-depth studies of low-dose OC formulations are mandatory to ascertain reduced metabolic risk of these OCs.

Carbohydrate metabolism in women who used oral contraceptives containing levonorgestrel or desogestrel: a 6-month prospective study

Blood glucose and pyruvate, plasma insulin, and glucagon levels as well as erythrocyte insulin receptors were measured during an oral glucose tolerance test in 38 normal women before and after 6 months' use of one of three new oral contraceptives containing low doses of 19 nortestosterone-derived progestogens, levonorgestrel, and desogestrel. A slight deterioration of glucose tolerance was observed, with the area under the glucose curve increasing by only 7%, 9%, and 12% after Ovidol (Aaciphar SA, Brussels, Belgium), Marvelon (Organon, SA, Brussels, Belgium), and Trigynon (Schering SA, Brussels, Belgium) administration, respectively. We did not find any argument in favor of the development of a state of insulin resistance in women using these compounds, because erythrocyte receptor binding was not modified and plasma insulin responses to glucose were decreased. The glucose-induced suppression of plasma glucagon levels seemed less effective for treatment with the desogestrel-containing preparations than with the levonorgestrel-containing oral contraceptives.

Carbohydrate metabolism during treatment with estrogen, progestogen, and low-dose oral contraceptives

The combination oral contraceptives have generally been shown to have an adverse effect on carbohydrate metabolism with resultant elevations of both blood glucose and insulin in users. Studies of the individual steroid components suggest that the estrogen is not at fault. The 19-norprogestins can produce these carbohydrate changes and seen to act at the insulin receptor level. Norgestrel, ethynodiol diacetate, and norethindrone alter carbohydrate metabolism, but norgestrel produces the most marked changes. Use of oral contraceptives containing less than 50 microgram of estrogen resulted in fewer metabolic changes than were seen with the drugs containing higher doses of estrogen.

Prospective studies of carbohydrate metabolism in "normal" women using norgestrel for eighteen months

Studies of carbohydrate metabolism were conducted before and after 18 months of daily use of a 0.075-mg norgestrel preparation by 50 "normal" women. Each study involved a 3-hour oral glucose tolerance test. There was a significant increase in the weights of the women over the time of study. In addition, all of the plasma insulin values and all of the blood glucose values were significantly elevated at the 18-month test. All of the control glucose tolerance tests were normal initially, but eight (16%) of the glucose curves were abnormal at the 18-month test. These data suggest a systemic metabolic effect of norgestrel which may play a role in accelerating atherogenesis.