Modification of plasma insulin-like growth factors and binding proteins during oral contraceptive use and the normal menstrual cycle

Reduced pericellular sensitivity to IGF-I in fibroblasts from girls with Turner syndrome: a mechanism to impair clinical responses to GH

Girls with Turner syndrome (TS) are treated with supraphysiological doses of growth hormone (GH) to improve final height; however in some girls, the growth response can be poor. This may reflect aberrations in GH and/or IGF-I actions at the cellular level, and thus this study compared the response of skin fibroblasts from normal children (n = 5) and girls with TS (n = 8) to GH, IGF-I, or a combination, by assessing the IGF binding protein (IGFBP) profile of conditioned medium harvested over 7 d. The two cell types had a comparable IGFBP profile; IGFBP-3 and IGFBP-4 were the most abundant species. TS fibroblasts produced more IGFBP-3 (d 7, 51.4 ± 45 ng/mL versus 20 ± 22 ng/mL; p < 0.05) than control cells; levels of IGFBP-4 were similar (21 ± 12 ng/mL versus 30 ± 21 ng/mL). GH did not influence IGFBP production. IGF-I treatment did not affect IGFBP-4 levels but enhanced the production of IGFBP-3 by both cell types (p < 0.05). However, the response of TS fibroblasts to IGF-I was approximately half that observed in normal cells (p < 0.05). Altered IGF-I activity, because of reduced bioavailability and/or reduced sensitivity, could contribute to the need for high GH doses in TS and for the poor response to GH in some girls with TS.

A cross-sectional study of different patterns of oral contraceptive use among premenopausal women and circulating IGF-1: implications for disease risk

Background

Insulin-like growth factor-1 (IGF-1) is important in normal growth, development, and homeostasis. Current use of oral contraceptives (OC) decreases IGF-1 concentrations; however, the effect of past use, age/timing of use, and type of OC used on IGF-1 levels is unknown. OC are the most commonly used form of birth control worldwide. Both IGF-1 and OC use have been linked to premenopausal breast and colorectal cancers, osteoporosis and cardiovascular disease (CVD). Understanding the effects of different patterns of OC use on IGF-1 levels may offer insight into its influence on disease risk in young women.

Methods

In a cross-sectional study of 328 premenopausal women ages 18 to 21 and 31 to 40 we examined the relationship between different patterns of OC use and circulating IGF-1 using adjusted linear regression analysis. Information on OC use was obtained through an interviewer administered questionnaire. Plasma IGF-1 was assessed with enzyme linked immunosorbent assay (ELISA).

Results

Among women aged 18 to 21, ever OC use was significantly associated with decreased IGF-1 levels compared to never use (β = -57.2 ng/ml, 95% confidence interval (CI): -88.7, -25.8). Among women aged 31 to 40, past users who first used OC at 25 years of age or older (β = 43.8 ng/ml, 95% CI: 8.8, 78.8), in the last 15 years (β = 35.1 ng/ml, 95% CI: 9.3, 61.0) or after 1995 (β = 46.6 ng/ml, 95% CI: 13.4, 79.8) had significantly higher IGF-1 levels compared to never users.

Conclusion

This is the first study to highlight the long term effects of OC use after cessation on IGF-1 levels among premenopausal women, which previously were thought to be transitory. Future studies of past use and IGF-1 levels are required and must consider age/timing of use and type/generation of OC used. Additional studies are needed to confirm the potential mediation of IGF-1 levels in the links between OC use and health outcomes.

Effects of oral contraceptives on diurnal profiles of insulin, insulin-like growth factor binding protein-1, growth hormone and cortisol in endurance athletes with menstrual disturbance

BACKGROUND

Menstrual disturbances in female athletes are often explained as a consequence of energy deficiency. Oral contraceptive (OC) treatment may have favorable metabolic effects. We evaluated effects of OCs on diurnal secretions of insulin, insulin-like growth factor binding protein 1 (IGFBP-1), growth hormone (GH) and cortisol in relation to changes in body composition in athletes with menstrual disturbance compared with regularly menstruating athletes and controls.

METHODS

Age- and BMI-matched groups of endurance athletes with menstrual disturbance (OAM, n = 9) and regularly cycling athletes (RM, n = 8) and sedentary controls (CTRL, n = 8) were examined, and hormone levels measured, before and after 8 months of treatment with a low-dose combined OC (30 µg ethinyl estradiol + 150 µg levonorgestrel).

RESULTS

Before OC treatment, the diurnal profile of insulin was lower (P < 0.01) and levels of IGFBP-1 (P < 0.05) and cortisol (P < 0.05) were higher in OAM athletes than in CTRL, whereas GH secretion was higher than in RM athletes (P < 0.05). After treatment, diurnal secretions of these hormones were similar between groups with an increase of IGFBP-1 in the regularly menstruating subjects only (P < 0.001). OC treatment increased body fat mass in OAM athletes (P < 0.01 versus baseline). The change in total fat mass correlated positively with pretreatment diurnal levels of GH (r_s = 0.67, P < 0.01) and cortisol (r_s = 0.64, P < 0.01).

CONCLUSIONS

OC treatment in endurance athletes with menstrual disturbance increases body fat mass and results in diurnal levels of insulin, IGFBP-1, GH and cortisol that are comparable to those in regularly menstruating subjects. These results suggest that OCs improve metabolic balance in OAM athletes.

Ethinyl oestradiol administration in women suppresses synthesis of collagen in tendon in response to exercise

Women are at greater risk than men of sustaining certain kinds of injury and diseases of collagen-rich tissues. To determine whether a high level of oestradiol has an acute influence on collagen synthesis in tendons at rest and in response to exercise, one-legged kicking exercise was performed for 60 min at 67% of maximum power by healthy, young oral contraceptive (OC) users when circulating synthetic (ethinyl) oestradiol was high (n = 11, HE-OC) and compared to similar women who had never used OCs when circulating endogenous oestrogen was low (n = 12, LE-NOC). Interstitial fluid was collected 24 h post-exercise through microdialysis catheters placed anterior to the patellar tendon in both legs and subsequently analysed for the amino-terminal propeptide of type I collagen (PINP), a marker of tendon collagen synthesis. To determine the long-term effect of OC usage, patellar tendon cross-sectional area (CSA) was measured by magnetic resonance imaging (MRI). A lower exercise-induced increase in tendon collagen synthesis was observed in HE-OC than in LE-NOC (DeltaPINP (mean +/- s.e.m.) 1.5 +/- 5.3 versus 24.2 +/- 9.4 ng ml(-1), P < 0.05). Furthermore, serum and the interstitial peritendinous tissue concentrations of insulin-like growth factor I (IGF-I) and IGF-binding proteins showed a reduced bioavailability in HE-OC compared with results in LE-NOC. No difference in patellar tendon CSA was observed between groups. In conclusion, the selective increase in tendon collagen synthesis in LE-NOC but not HE-OC 24 h post-exercise is consistent with the hypothesis that oestradiol inhibits exercise-induced collagen synthesis in human tendon. The mechanism behind this is either a direct effect of oestradiol, or an indirect effect via a reduction in levels of free IGF-I. However, the data did not indicate any long-term effect on tendon size associated with chronic OC use.

Modulation of the growth hormone-insulin-like growth factor (GH-IGF) axis by pharmaceutical, nutraceutical and environmental xenobiotics: an emerging role for xenobiotic-metabolizing enzymes and the transcription factors regulating their expression. A review

The growth hormone-insulin-like growth factor (GH-IGF) axis has gained considerable focus over recent years. One cause of this increased interest is due to a correlation of age-related decline in plasma GH/IGF levels with age-related degenerative processes, and it has led to the prescribing of GH replacement therapy by some practitioners. On the other hand, however, research has also focused on the pro-carcinogenic effects of high GH-IGF levels, providing strong impetus for finding regimes that reduce its activity. Whereas the effects of GH/IGF activity on the action of xenobiotic-metabolizing enzyme systems is reasonably well appreciated, the effects of xenobiotic exposure on the GH-IGF axis has not received substantial review. Relevant xenobiotics are derived from pharmaceutical, nutraceutical and environmental exposure, and many of the mechanisms involved are highly complex in nature, not easily predictable from existing in vitro tests and do not always predict well from in vivo animal models. After a review of the human and animal in vivo and in vitro literature, a framework for considering the different levels of direct and indirect modulation by xenobiotics is developed herein, and areas that still require further investigation are highlighted, i.e. the actions of common endocrine disruptors such as pesticides and phytoestrogens, as well as the role of xenobiotic-metabolizing enzymes and the transcription factors regulating their expression. It is anticipated that a fuller appreciation of the existing human paradigms for GH-IGF axis modulation gained through this review may help explain some of the variation in levels of plasma IGF-1 and its binding proteins in the population, aid in the prescription of particular dietary regimens to certain individuals such as those with particular medical conditions, guide the direction of long-term drug/nutraceutical safety trials, and stimulate ideas for future research. It also serves to warn athletes that using compounds touted as performance enhancing because they promote short-term GH release could in fact be detrimental to performance in the long-run.

Treatment with combined oral contraceptives induces a rise in serum C-reactive protein in the absence of a general inflammatory response

BACKGROUND

The role of inflammation in the pathogenesis of cardiovascular disease is well established. C-reactive protein (CRP) is the strongest independent predictor of myocardial infarction and stroke in women. Recent studies have indicated that CRP levels are raised during use of combined oral contraceptives (COCs).

OBJECTIVES

The aim of the study was to investigate the effect of COCs on serum CRP levels and to indicate the underlying mechanisms of an expected increase.

METHOD

In a prospective randomized cross over-study 35 women used two different preparations of COC, one second and one third generation. Serum levels of CRP, serum amyloid A (SAA), interleukin-6 (IL-6), tumor necrosis factor alpha (TNFalpha), antibodies against oxidized LDL, insulin and insulin-like growth factor-I (IGF-I) along with insulin-like growth factor binding protein-1 (IGFBP-1) and IGFBP-3 were analyzed before and during the two treatments. E-selectin, von Willebrand factor and factor VIII concentrations in plasma were also measured.

RESULTS

A rise in serum CRP was observed during both treatments; the median level increased from 0.45 mg L(-1) at baseline to 1.48 mg L(-1) with second generation and to 2.02 mg L(-1) with third generation COC. The serum levels of SAA increased slightly during treatment with the third generation COC. IL-6 and TNFalpha were unaffected by treatment. Both preparations lowered IGF-I and raised IGFBP-1 and IGFBP-3 concentrations.

CONCLUSION

The raised serum CRP concentration during treatment with COCs appears to be related to a direct effect on hepatocyte CRP synthesis and does not reflect IL-6 mediated inflammation, endothelial activation or induction of insulin resistance.

Ethinylestradiol and testosterone have divergent effects on circulating IGF system components in adolescents with constitutional tall stature

OBJECTIVE

Pharmacological doses of estrogens or testosterone are used to limit the final height of girls or boys with constitutional tall stature but the mechanism behind this growth inhibition is still debated. We therefore studied the changes in the circulating components of the insulin-like growth factor (IGF) system during high dose sex steroid therapy.

DESIGN AND METHODS

Twenty three girls and twenty boys with constitutional tall stature were treated with 100 microg ethinylestradiol per day or 250 mg testosterone ester every 14 days respectively. In 19 girls and 18 boys, the levels of IGF-I, free IGF-I, IGF-II, acid-labile subunit (ALS) and IGF binding proteins (IGFBP)-2 to -6 were measured before and 3-6 months after the start of therapy (group 1). In 18 girls and 11 boys, samples were collected at the end of therapy and 3 to 6 months afterwards (group 2). Fourteen girls and nine boys belonged to both groups. All parameters were measured by radioimmunoassay or ELISA.

RESULTS

Levels of IGF-I were decreased significantly by estrogen treatment but remained unchanged during testosterone treatment. Free IGF-I decreased during estrogen treatment but increased during testosterone therapy. Estrogens increased IGF-II and testosterone reduced it. The important reduction of IGFBP-2 during estrogen therapy is not reproduced by androgen therapy, neither is the stimulation by estrogens of IGFBP-4. IGFBP-3 is not modulated by either sex steroid. We found that IGFBP-6 is up-regulated by testosterone but not by estrogens; the reverse is true for ALS, which increased during estrogen treatment but remained unchanged during testosterone treatment.

CONCLUSIONS

Our findings demonstrate that androgens and estrogens exert differential effects on the circulating levels of several IGF components.

Combined oral contraceptives in the treatment of polycystic ovary syndrome

Combined oral contraceptives (COC) are the most often used treatment modality for polycystic ovary syndrome (PCOS). Undisputedly, COC suppress androgen production, thus ameliorating skin androgenic symptoms and improving menstrual dysfunction. On the other hand, there are still many unresolved issues concerning their metabolic effects. COC could decrease insulin sensitivity and deteriorate glucose tolerance, although the negative influence on insulin sensitivity is dependent on other factors (especially obesity) and this need not be expressed in non-obese patients. It is probable that the impairment of glucose tolerance is reversible, as the incidence of diabetes is not increased in past COC users. The effects of COC on the lipid spectrum are dependent on the type of gestagen, but lipid levels usually remain within the reference limits. Combination therapy of COC with weight reduction or insulin sensitizers could further suppress androgen levels and improve metabolic parameters. The establishment of COC after laparoscopic ovarian drilling may further decrease androgen levels. The combination of COC and GnRH analogues is not superior to COC therapy alone. Prospective data about the influence of COC on the risk of diabetes mellitus, coronary artery disease and endometrial cancer in PCOS women are lacking.

Polymorphisms and Circulating Levels in the Insulin-Like Growth Factor System and Risk of Breast Cancer: A Systematic Review

We reviewed all English-language articles on associations among circulating levels of the insulin-like growth factors (IGF) and their binding proteins (IGFBP), polymorphisms in their genes, and breast cancer risk. In premenopausal women, five of eight IGF-I studies and four of six IGFBP-3 studies of circulating levels found that women in the highest quantile had more than twice the risk of developing breast cancer of those in the lowest, although in some this effect was only apparent at young ages. In postmenopausal women, however, there was no consistent effect. A simple sequence length polymorphism 1 kb 5′ to IGF-I was examined in relation to circulating levels of IGF-I (12 studies) or breast cancer risk (4 studies), but there was no convincing evidence of any effect. For an A/C polymorphism 5′ to IGFBP-3, all three studies were consistent with a modest effect on circulating levels, but no evidence of a direct effect on breast cancer risk was seen in the only relevant study. Variation within the reference range of IGF-I and IGFBP-3 may confer only modest increases in breast cancer risk, and any single polymorphism may only account for a small proportion of that variation. Nevertheless, population attributable fractions for high circulating levels of IGF-I and IGFBP-3 and for common genetic variants could be substantial. Further large studies, or combined analysis of data from existing studies, are needed to quantify these effects more precisely.

Markers for cardiovascular disease in monozygotic twins discordant for the use of third-generation oral contraceptives

Oral contraceptives (OC) modulate the risk for developing cardiovascular (CV) diseases. The aim of this study was to determine whether the use of third-generation OC has an impact on markers of CV disease in genetically identical women. We performed an intrapair comparison in 27 monozygotic twin pairs, one of whom was taking third-generation OC, whereas the other was not using OC. Biometric parameters were ascertained and conventional and 24-h ambulatory blood pressure (BP) was recorded. A fasting blood sample was taken for the measurement of glucose, insulin, proinsulin, lipids, and insulin-like growth factor binding protein-1 (IGFBP-1). Insulin resistance and beta-cell function were calculated by homeostasis model assessment (HOMA). A 24-h urine sample for cortisol was obtained. Third-generation OC use increased 24-h ambulatory systolic and diastolic BP by 5.2 and 3.9 mmHg, respectively (both P=0.0003). There was no effect on glucose, insulin and proinsulin levels, and on HOMA parameters, but the IGFBP-1 levels were markedly raised (P=0.0009). The lipid profile showed a 34% increase in triglyceride levels (P < 0.0001), but also a 7% increase in HDL-cholesterol levels (P=0.037). Use of third-generation OC impacts on CV disease markers in young-adult genetically identical women. Some changes are beneficial (increased HDL-cholesterol), whereas others may be deleterious (increased BP and triglyceride levels) or have unknown effects at this time (increased IGFBP-1 levels).

Reduced free IGF-I and increased IGFBP-3 proteolysis in Turner syndrome: modulation by female sex steroids

The bioactivity of the growth hormone-insulin-like growth factor (IGF) system is reduced in Turner syndrome and may explain the reduction seen in final height. We compared levels of free and total IGF-I, immunoreactive and Western ligand blot IGF-binding protein (IGFBP)-3, and IGFBP-3 proteolysis in women with Turner syndrome (n = 23) before (T(B)) and during 6 mo treatment with 17beta-estradiol and norethisterone. An age-matched group of controls (n = 24) was included. Total IGF-I and immunoreactive levels of IGFBP-3 were comparable in T(B) and controls, whereas free IGF-I (P = 0.02) in T(B) was less than in controls. Western ligand blotting (WLB)-IGFBP-3 was significantly lower in T(B) than in controls (P = 0.0005). Accordingly, IGFBP-3 proteolysis was greater in Turner syndrome (P = 0.001). Female sex steroid treatment increased WLB-IGFBP-3 (P = 0.0005), whereas immunoreactive IGFBP-3 and IGFBP-3 proteolysis were normalized (P = 0.004). Free IGF-I remained unchanged (P = 0.8), with a tendency toward a decrease in total IGF-I (P = 0.1). In conclusion, despite normal total IGF-I and immunoreactive IGFBP-3, free serum IGF-I is less and IGFBP-3 proteolysis is greater in Turner syndrome than in controls. During sex steroid treatment, IGFBP-3 proteolysis normalized, without any change in free IGF-I.

Effects of soy isoflavones on markers of bone turnover in premenopausal and postmenopausal women

Soy isoflavones are hypothesized to exert hormonal effects in women and thus may play a role in bone metabolism throughout life. In 2 randomized, cross-over studies, 14 pre- and 17 postmenopausal women were given 3 soy protein isolates containing different amounts of isoflavones [control, 0.13; low isoflavone (low-iso), 1.00; and high-iso, 2.01 mg/kg body wt/day, averaging 8, 65, and 130 mg/day, respectively], for over 3 months each. Food records, blood samples, and 24-h urine collections were obtained throughout the studies. The endpoints evaluated included plasma or serum concentrations of bone-specific alkaline phosphatase, osteocalcin, insulin-like growth factor-I (IGFI), IGF binding protein-3 (IGFBP3), and urine concentrations of deoxypyridinoline cross-links and carboxy-terminal telopeptide of type I collagen. In premenopausal women, IGFI and IGFBP3 concentrations were increased by the low-iso diet, and deoxypyridinoline cross-links was increased by both the low- and high-iso diets during certain phases of the menstrual cycle. In postmenopausal women, bone-specific alkaline phosphatase was decreased by both the low- and high-iso diets, and there were trends toward decreased osteocalcin, IGFI, and IGFBP3 concentrations with increasing isoflavone consumption. Although soy isoflavones do affect markers of bone turnover, the changes observed were of small magnitude and not likely to be clinically relevant. These data do not support the hypothesis that dietary isoflavones per se exert beneficial effects on bone turnover in women.