Alterations in the insulin-like growth factor system during the menstrual cycle in normal women

IGF-I and IGFBP-1 in Relation to Body Composition and Physical Performance in Female Olympic Athletes

INTRODUCTION

Insulin- like growth factor-I (IGF-I) is an anabolic hormone that may affect athletic performance in female athletes, and insulin-like growth factor binding protein-1 (IGFBP-1) is an important regulator of bioactive IGF-I. There is limited knowledge of the role of endogenous IGF-I and IGFBP-1 for body composition and physical performance in female elite athletes.

PURPOSE

To examine IGF-I, age adjusted IGF-I (IGFSD), IGFBP-1 and insulin in female Olympic athletes compared with controls and different sport categories, and in relation to body composition and physical performance in the athletes.

METHODS

Female athletes (n=103) and untrained controls (n=113) were included in this cross-sectional study. Body composition was established by dual-energy X-ray absorptiometry. Serum IGF-I and IGFBP-1 were analyzed by radioimmunoassay and IGFSD was calculated. Insulin was analyzed by electrochemiluminescence immunoassay. Athletes were offered to participate in standardized physical fitness tests.

RESULTS

The athletes demonstrated significantly higher IGF-I, IGFSD and IGFBP-1 and lower insulin levels than controls (p<0.05, p<0.05, p<0.01, p<0.001 respectively). Power athletes had significantly higher IGFSD compared to both endurance and technical athletes (p<0.05, p<0.01, respectively). In athletes and controls combined, significant positive correlations were found between IGF variables and higher bone mineral density (BMD) and lean mass and lower fat percent. IGF-I was positively correlated with squat jump (r_s = 0.28, p<0.05) and IGFBP-1 correlated positively with squats (r_s =0.35, p<0.05).

CONCLUSION

We found higher IGF-I, IGFSD and IGFBP-1 in female athletes than controls, and the highest IGFSD in power athletes. IGF-I and IGFBP-1 were related to increased BMD and lean mass and lower fat percent, as well as were positively associated with physical fitness tests. Future studies are needed to elucidate if these results reflect adaptive responses to physical activity or genetic predisposition.

A summary of the influence of exogenous estrogen administration across the lifespan on the GH/IGF-1 axis and implications for bone health

Bone growth, development, and remodeling are modulated by numerous circulating hormones. Throughout the lifespan, the extent to which each of the hormones impacts bone differs. Understanding the independent and combined impact of these hormones on controlling bone remodeling allows for the development of more informed decision making regarding pharmacology, specifically the use of hormonal medication, at all ages. Endocrine control of bone health in women is largely dictated by the growth hormone (GH)/insulin-like growth factor-1 (IGF-1) axis and the hypothalamic-pituitary-ovarian (HPO) axis. Growth hormone, secreted from the pituitary gland, stimulates cells in almost every tissue to secrete IGF-1, although the majority of circulating IGF-1 is produced hepatically. Indeed, systemic IGF-1 concentrations have been found to be correlated with bone mineral density (BMD) in both pre- and post-menopausal women and is often used as a marker of bone formation. Sex steroids produced by the ovaries, namely estradiol, mediate bone resorption through binding to estrogen receptors on osteoclasts and osteoblasts. Specifically, by increasing osteoclast apoptosis and decreasing osteoblast apoptosis, adequate estrogen levels prevent excessive bone resorption, which helps to explain the rapid decline in bone mass that occurs with the menopausal decrease in estrogen production. Though there are documented correlations between endogenous estrogen concentrations and GH/IGF-1 dynamics, this relationship changes across the lifespan as sex-steroid dynamics fluctuate and, possibly, as tissue responsiveness to GH stimulation decreases. Aside from the known role of endogenous sex steroids on bone health, the impact of exogenous estrogen administration is of interest, as exogenous formulations further modulate GH and IGF-1 production. However, the effect and extent of GH and IGF-1 modulation seems to be largely dependent on age at administration and route of administration. Specifically, premenopausal women using combined oral contraceptive therapy (COC), post-menopausal women taking oral hormone therapy (HT), and both pre- and post-menopausal women using a transdermal form of estrogen therapy (COC or HT) demonstrate disparate GH/IGF-1 responses to exogenous estrogen. This review serves to summarize what is currently known regarding the influence of exogenous estrogen administration across the lifespan on the GH/IGF-1 axis and implications for bone health.

A prospective study of insulin-like growth factor 1, its binding protein 3, and risk of endometriosis

Several retrospective case-control studies suggested that insulin-like growth factor 1 (IGF-1) or insulin-like growth factor binding protein 3 (IGFBP-3) was associated with endometriosis. However, results are inconsistent and no prospective study exists. We prospectively evaluated associations between plasma levels of IGF-1 and IGFBP-3 and laparoscopically confirmed endometriosis in a case-control study nested within the Nurses' Health Study II. Between blood collections in 1996-1999 and 2007, we ascertained 310 premenopausal women with incident endometriosis and 615 matched controls. We estimated incidence rate ratios and 95% confidence intervals using multivariable conditional logistic regression. We observed no statistically significant associations between endometriosis and IGF-1 (incidence rate ratio (IRR) = 0.88, 95% confidence interval (CI): 0.61, 1.27; Ptrend = 0.48), IGFBP-3 (IRR = 1.12, 95% CI: 0.80, 1.57; Ptrend = 0.51), and the IGF-1:IGFBP-3 molar ratio (IRR = 0.94, 95% CI: 0.66, 1.34; Ptrend = 0.64), comparing the top with the bottom tertile. IGF-1, IGFBP-3, and the molar ratio appeared to be positively associated with endometriosis risk among women aged <40 years at blood draw (IGF-1: IRR = 1.60, 95% CI: 0.86, 2.98; IGFBP-3: IRR = 1.85, 95% CI: 1.08, 3.16; IGF-1:IGFBP-3: IRR = 1.57, 95% CI: 0.85, 2.88) but not among women aged ≥40 years at blood draw (all Pheterogeneity ≤ 0.05). Overall, these data suggest that, if IGF-1 or IGFBP-3 plays a role in the etiology of endometriosis, it is minimal and perhaps only among younger women.

Prognostic effect of menstrual cycle on timing of surgery in premenopausal breast cancer patients

BACKGROUND

It is controversial whether surgery during different menstrual phases (a kind of host milieu may influence biological characteristics of micrometastatic foci) affects clinical outcomes.

METHODS

Survival outcomes were compared between patients who underwent surgery during the follicular (cycle days 1 to 14) and luteal (days 15 to 31) phases. A range of cutoff days from day 10 to 22 was used to observe the risk trend.

RESULTS

The follicular phase was associated with a more favorable prognosis than the luteal phase in disease-free survival (DFS) [hazard ratio (HR) .318, 95% confidence interval (CI) .10 to .99, P = .049] and overall survival (OS) (HR .260, 95% CI .07 to .92, P = .036). Similar results were detected when the cutoff day was set at days 14, 18, and 19 in DFS and days 11, 13, and 14 in OS. A low HR flat fluctuation was observed from cutoff days 10 to 22, and the risk went up thereafter for both DFS and OS.

CONCLUSION

Surgery performed during the follicular phase provides a more favorable prognosis compared with the luteal phase.

Body size in early life and adult levels of insulin-like growth factor 1 and insulin-like growth factor binding protein 3

Body size in early life has been associated with breast cancer risk. This may be partly mediated through the insulin-like growth factor (IGF) pathway. The authors assessed whether birth weight, body fatness at ages 5 and 10 years, and body mass index (BMI; weight (kg)/height (m)(2)) at age 18 years were associated with plasma concentrations of insulin-like growth factor 1 (IGF-1) and insulin-like growth factor binding protein 3 in 6,520 women aged 32-70 years at blood draw from the Nurses' Health Study (1990-2006) and Nurses' Health Study II (1997-2005). Birth weight, body fatness in childhood, and BMI at age 18 years were inversely associated with adult IGF-1 levels. For example, IGF-1 levels were 11.9% lower in women who reported being heaviest at age 10 years than in those who were leanest at age 10 (P-trend < 0.0001). Further, women who reported their birth weight as ≥10 pounds (≥4.5 kg) (vs. <5.5 pounds (<2.5 kg)) had 7.9% lower IGF-1 levels (P-trend = 0.002). Women whose BMI at age 18 years was ≥30 (vs. <20) had 14.1% lower IGF-1 levels (P-trend < 0.0001). Similar inverse associations were observed for insulin-like growth factor binding protein 3. These observations did not vary by adult BMI or menopausal status at blood draw. These findings suggest that altered IGF-1 levels in adulthood may be a mechanism through which early-life body size influences subsequent breast cancer risk.

Reproductive aging and its consequences for general health

Reproductive aging coincides with endocrine changes that are not solely reproductive in nature and culminates in hypergonadotropic hypogonadism and amenorrhea. These changes are identifiable biochemically regardless of clinical manifestations. Changes in the hypothalamic-pituitary-ovarian axis are associated with changes in other hormonal axes, specifically the adrenal androgen and the somatotropic axis. A large body of literature indicates that reproductive aging is associated with a decline in the somatotropic axis. The interactions between reproductive aging and changes in the adrenal androgen axis are more complex and complicated by age-related declines in the adrenal axis early in the reproductive years. These changes may play an important role in overall health maintenance. Attempts to ameliorate hormonal declines with exogenous hormonal therapy have produced mixed results. Finally, the age-specific timing as well as the rapidity of the changes that occur with reproductive aging seems to have important consequences on metabolism, cardiovascular risk, cognition, bone density, and even mortality.

Effects of high-intensity resistance training in patients with rheumatoid arthritis: a randomized controlled trial

OBJECTIVE

To confirm, in a randomized controlled trial (RCT), the efficacy of high-intensity progressive resistance training (PRT) in restoring muscle mass and function in patients with rheumatoid arthritis (RA). Additionally, to investigate the role of the insulin-like growth factor (IGF) system in exercise-induced muscle hypertrophy in the context of RA.

METHODS

Twenty-eight patients with established, controlled RA were randomized to either 24 weeks of twice-weekly PRT (n = 13) or a range of movement home exercise control group (n = 15). Dual x-ray absorptiometry-assessed body composition (including lean body mass [LBM], appendicular lean mass [ALM], and fat mass); objective physical function; disease activity; and muscle IGFs were assessed at weeks 0 and 24.

RESULTS

Analyses of variance revealed that PRT increased LBM and ALM (P < 0.01); reduced trunk fat mass by 2.5 kg (not significant); and improved training-specific strength by 119%, chair stands by 30%, knee extensor strength by 25%, arm curls by 23%, and walk time by 17% (for objective function tests, P values ranged from 0.027 to 0.001 versus controls). In contrast, body composition and physical function remained unchanged in control patients. Changes in LBM and regional lean mass were associated with changes in objective function (P values ranged from 0.126 to <0.0001). Coinciding with muscle hypertrophy, previously diminished muscle levels of IGF-1 and IGF binding protein 3 both increased following PRT (P < 0.05).

CONCLUSION

In an RCT, 24 weeks of PRT proved safe and effective in restoring lean mass and function in patients with RA. Muscle hypertrophy coincided with significant elevations of attenuated muscle IGF levels, revealing a possible contributory mechanism for rheumatoid cachexia. PRT should feature in disease management.

Genetic variation and circulating levels of IGF-I and IGFBP-3 in relation to risk of proliferative benign breast disease

Insulin-like growth factor-I (IGF-I) and its major binding protein IGFBP-3 have been implicated in breast carcinogenesis. We examined the associations between genetic variants and circulating levels of IGF-I and IGFBP-3 with proliferative benign breast disease (BBD), a marker of increased breast cancer risk, in the Nurses' Health Study II (NHSII). Participants were 359 pathology-confirmed proliferative BBD cases and 359 matched controls. Circulating IGF-I and IGFBP-3 levels were measured in blood samples collected between 1996 and 1999. Thirty single nucleotide polymorphisms (SNPs) in IGF-I, IGFBP-1, and IGFBP-3 genes were selected using a haplotype tagging approach and genotyped in cases and controls. Circulating IGF-I levels were not associated with proliferative BBD risk. Higher circulating IGFBP-3 levels were significantly associated with increased risk of proliferative BBD (highest vs. lowest quartile odds ratio (OR) [95% confidence interval (CI)], 1.70 (1.06-2.72); p-trend = 0.03). The minor alleles of 2 IGFBP-3 SNPs were associated with lower proliferative BBD risk (homozygous variant vs. homozygous wild-type OR (95% CI): rs3110697: 0.6 (0.4-0.9), p-trend = 0.02; rs2132570: 0.2 (0.1-0.6), p-trend = 0.02). Three other IGFBP-3 SNPs (rs2854744, rs2960436 and rs2854746) were significantly associated with circulating IGFBP-3 levels (p < 0.01). Although these SNPs were not significantly associated with proliferative BBD risk, there was suggestive evidence that the alleles associated with higher circulating IGFBP-3 levels were also associated with higher risk of proliferative BBD. These results suggest that genetic variants and circulating levels of IGFBP-3 may play a role in the early stage of breast carcinogenesis.

Insulin-like growth factor-I, insulin-like growth factor binding protein-3 and the risk of fibrocystic breast conditions among Chinese women

We investigated whether circulating insulin-like growth factor-I (IGF-I) and insulin-like growth factor binding protein-3 (IGFBP-3) levels are associated with the risk of fibrocystic breast conditions (FBC), in a case-control study nested within a randomized trial of breast self-examination conducted in Shanghai, China. Participants were enrolled during 1989-1991 and were followed over 10 years for the development of breast diseases. Controls (n = 897) were frequency-matched by age to cases (n = 451), who were diagnosed with FBC between 1995 and 2000. Circulating IGF-I and IGFBP-3 levels and their molar ratio were positively associated with risk of FBC. The odds ratios (ORs) and 95% confidence intervals (CI) for the upper fourth of the distribution compared to the lowest fourth for IGF-I, IGFBP3 and their molar ratio were 3.02 (2.02-4.52), 1.92 (1.37-2.71) and 2.26 (1.52-3.36), respectively. The strength of the association between IGF-I levels and FBC was attenuated after adjustment for IGFBP-3 and that for IGFBP-3 was largely eliminated after adjustment for IGF-I. Increasing levels of IGF-I were particularly associated with increasing risk of FBC with proliferative elements (ORs and 95% CIs for the 2nd, 3rd and upper fourth of the distribution of IGF-I: 3.13 (1.50-6.53), 4.57 (2.22-9.39) and 6.30 (3.08-12.89), compared with the lowest fourth. Our results suggest that elevated levels of IGF-I may contribute to the development of FBC.

Short-term phytoestrogen supplementation alters insulin-like growth factor profile but not lipid or antioxidant status

Phytoestrogens are plant compounds that have been proposed to have a variety of health benefits. The aim of this study was to assess the effects of these compounds on a number of physiological endpoints. Subjects were given a single intake of a phytoestrogen-rich (80 mg total phytoestrogens) supplement containing soy, rye and linseed (Phase 1), followed by a week-long intervention using the same supplement (Phase 2) (80 mg total phytoestrogens daily). A number of biochemical endpoints were assessed including urinary phytoestrogen metabolites, lipids, antioxidant status, DNA damage and insulin-like growth factor-1 (IGF-1) and IGF binding protein-1 (IGFBP-1) and -3 (IGFBP-3). Ten healthy female subjects took part in the study. Excretion of the isoflavones genistein, daidzein and equol in urine increased in both phases of the study. No other endpoint was altered in Phase 1. However, in Phase 2, concentrations of IGF-1 and IGFBP-3 were increased by phytoestrogen supplementation [IGF-1, median (IQ range), baseline 155 (123, 258), postweek 265 (228, 360) ng/ml, P<.05; IGFBP-3, baseline 3725 (3631, 4196), postweek 4420 (4192, 4935) ng/ml, P<.05]. There was no effect of supplementation on lipids or markers of antioxidant status. Short-term phytoestrogen supplementation increases urinary phytoestrogen excretion and increases IGF-1 and IGFBP-3. These results require elucidation in further controlled studies.

Effect of red clover-derived isoflavone supplementation on insulin-like growth factor, lipid and antioxidant status in healthy female volunteers: a pilot study

BACKGROUND

Isoflavones are estrogen-like plant compounds that may protect against cardiovascular disease and endocrine-responsive cancer. Isoflavones may, because of their ability to act as selective estrogen receptor modulators, alter insulin-like growth factor (IGF) status.

OBJECTIVE

The aim of this study was to assess the effect of 1-month isoflavone supplementation (86 mg/day red clover-derived isoflavones) on IGF status.

DESIGN AND SUBJECTS

Healthy pre- (n=16) and postmenopausal (n=7) women were invited to take part in a randomised, placebo-controlled crossover study with a minimum 2-month washout period.

RESULTS

: For premenopausal subjects, the change in IGF-1, IGF-BP1 and IGF-BP3 assessed at different points of the menstrual cycle did not differ between isoflavone and placebo phase. However, the change in IGF-1, when examined pre- and post-supplementation, was nonsignificantly reduced (P=0.06) on the isoflavone supplement compared to placebo. For postmenopausal subjects, the change in IGF-1, IGF-BP1 and IGFBP-3 concentrations over the supplementation period did not differ between isoflavone or placebo phase. Isoflavones increased HDL in postmenopausal women compared to placebo (P=0.02) but did not alter either cholesterol or triacylglycerol concentrations, and had no effect on antioxidant status.

CONCLUSIONS

This study shows that 1-month supplementation with red clover isoflavones has a positive effect on HDL cholesterol, but at most a small effect on IGF status in premenopausal and no effect in postmenopausal subjects. Further studies are required to ascertain the role these dietary compounds may have to play in breast cancer prevention.

Changes in the local regulation of insulin-like growth factors I and II and insulin-like growth factor-binding proteins in osteoarthritis of the canine stifle joint secondary to cruciate ligament rupture

OBJECTIVES

To investigate changes in concentrations of insulin-like growth factors I (IGF-I) and II (IGF-II) and the expression of IGF-binding proteins (IGFBP) in synovial fluids from dogs with naturally occurring osteoarthritis (OA) of the canine stifle joint secondary to cranial cruciate ligament (CCL) rupture.

STUDY DESIGN

Prospective study with synovial fluid sampling from diseased and contralateral unaffected joints at 0, 1.5, and 5 months.

SAMPLE POPULATION

Eleven dogs with unilateral CCL deficiency, with unaffected contralateral joints.

METHODS

IGF-I and IGF-II concentrations in synovial fluids were estimated by radioimmunoassay at 0, 1.5, and 5 months; Western ligand blotting was performed for intact IGFBPs at 0, 1.5, 5, and 9 months. Both stifle joints were radiographed at 0, 7, and 13 months.

RESULTS

The IGF system is altered after CCL rupture and during development of early OA. Mean IGF-I and IGF-II concentrations in index stifle joints at study entry were 201.6 microg/mL and 345.7 microg/mL, respectively, compared with 57.7 microg/mL and 79.4 microg/mL, respectively, for contralateral joints. Index joint IGF concentrations increased after surgical treatment and then declined, although they remained higher than contralateral joints. Index joints had increases in IGFBP-3 and -4, and a decrease in IGFBP-2 expression compared with contralateral joints.

CONCLUSIONS

Although IGF concentrations are increased in canine OA, alterations in IGFBP profiles may limit the tissue availability of IGF.

CLINICAL RELEVANCE

Manipulation of the IGF system may provide an opportunity for novel treatments of OA in dogs.

The somatotropic axis in short children born small for gestational age: relation to insulin resistance

To determine whether hyperinsulinemia and reduced insulin sensitivity in individuals born small for gestational age (SGA) could be related to persisting abnormalities of the GH/IGF-I axis, we assessed overnight GH secretory profiles and measured fasting glucose, insulin, intact and 32,33 split proinsulin, and IGF-I levels in 16 short SGA children (age range 2.3-8.0 y) and in controls. Insulin sensitivity was calculated using the homeostasis model. Compared with short normal-birthweight controls (n = 7, age range 2.3-5.0 y), short SGA children had higher fasting insulin levels (means: 26.8 vs 20.6 pmol/L, p = 0.02), lower insulin sensitivity [means: 204 vs 284 %homeostasis model assessment (HOMA), p = 0.01], and higher beta cell function (112 vs 89 %HOMA, p = 0.04). SGA children also had lower levels of IGFBP-1 (87.0 vs 133.8, p = 0.04), but similar IGF-I levels (IGF-I SDS: -1.1 vs -1.7, p = 0.4). Compared with normal-height controls (n = 15, age range 5.6-12.1 y), SGA children had higher overnight GH secretion (GH maximum: 55.9 vs 39.6 mU/L, p = 0.01; mean: 13.1 vs 8.9, p = 0.004; minimum: 1.2 vs 0.6, p = 0.02). Interestingly, among SGA children, fasting insulin levels and insulin sensitivity were significantly related to overnight GH secretion (insulin sensitivity vs maximum GH: r = -0.68, p = 0.01; vs GH pulse amplitude r = -0.71, p = 0.007). The only hormone level significantly related to current height velocity was C-peptide (r = 0.75, p = 0.008). In conclusion, elevated fasting insulin levels and reduced insulin sensitivity in short SGA children was related to elevated levels of overnight GH secretion. We hypothesize that resistance to the somatotropic actions of GH and IGF-I in short SGA children may contribute directly to reduced insulin sensitivity.

Clinical features in women with polycystic ovaries: relationships to insulin sensitivity, insulin gene VNTR and birth weight

OBJECTIVE

Polycystic ovaries are a common ultrasound finding, yet few of these women have many clinical features of polycystic ovary syndrome. Clinical presentation may relate to degree of insulin resistance, common polymorphism at the insulin gene VNTR, and birth weight. We therefore examined the relationship between insulin sensitivity, insulin gene VNTR genotype, birth weight and presence of polycystic ovaries/features of polycystic ovary syndrome in a normal population study.

DESIGN AND PATIENTS

In 224 young women recruited as normal volunteers, ovarian morphology was determined by transabdominal ultrasound and features of polycystic ovary syndrome were identified on clinical and biochemical examination. Insulin sensitivity was estimated from fasting glucose and insulin levels using the homeostasis model. Insulin gene VNTR genotypes were determined in women and their parents.

MEASUREMENTS AND RESULTS

Thirty-three per cent (74/224) had polycystic ovaries on ultrasound. These women had higher birth weights (P = 0.004), higher insulin sensitivity (P = 0.02) and higher leptin levels for body mass index (P = 0.04) than women with normal ovaries. However among women with polycystic ovaries, increasing severity of clinical phenotype (based on number of features of: menstrual irregularity, acne, hirsutism, serum testosterone > 3 mmol/l and LH > 10 IU/l) was associated with decreasing insulin sensitivity (P < 0.0001) and related to paternally transmitted insulin gene VNTR class III alleles (P = 0.03).

CONCLUSION

Women with polycystic ovaries on ultrasound have increased insulin sensitivity and possible leptin resistance, which could predispose to future weight gain. However, in these women the appearance of clinical features of polycystic ovary syndrome is related to insulin resistance and insulin gene VNTR class III alleles.

IGF status is altered by tamoxifen in patients with breast cancer

AIMS

An increased concentration of insulin-like growth factor 1 (IGF-1) is an independent risk factor for premenopausal breast cancer. Tamoxifen is thought initially to reduce concentrations of IGF-1 and increase concentrations of the IGF binding proteins. The aim of this study was to compare concentrations of IGF-1, IGF binding protein 1 (IGF-BP1), and IGF-BP3 in patients with breast cancer (n = 14) with those seen in control subjects (n = 23) and to assess the effect of tamoxifen on IGF status in these patients.

METHODS

Non-fasting blood samples were collected from patients with breast cancer before surgery and after nine, 18, and 27 months of tamoxifen treatment. The baseline concentrations were compared with those of age and sex matched healthy control subjects.

RESULTS

IGF-1, IGF-BP3, and IGF-BP1 concentrations were not significantly different in cases and controls. Tamoxifen treatment significantly increased IGF-BP1 after 18 and 27 months (baseline: mean, 21.6 ng/ml; SD, 16.6; 18 months: mean, 52.0 ng/ml; SD, 41.8; p = 0.019; 27 months: mean, 40.7 ng/ml; SD, 24.9; p = 0.043) and IGF-BP3 after nine, 18, and 27 months (baseline: mean, 3119 ng/ml; SD, 507; nine months: mean, 3673 ng/ml; SD, 476; p = 0.004; 18 months: mean, 3445 ng/ml; SD, 634; p = 0.034; 27 months: 3409 ng/ml; SD, 501; p = 0.043) when compared with baseline values. IGF-1 was not altered significantly from baseline at any time point. However, the IGF-1 to IGF-BP3 ratio was significantly decreased at both nine and 18 months (baseline: mean, 0.058; SD, 0.014; nine months: mean, 0.039; SD, 0.008; p = 0.033; 18 months: mean, 0.044; SD, 0.012; p = 0.01). This ratio was not significantly different from baseline at 27 months (mean, 0.054; SD, 0.01; p = 0.08).

CONCLUSIONS

Tamoxifen increases IGF-BP3 and IGF-BP1 concentrations. It also decreases the IGF-1 to IGF-BP3 ratio but this effect may be limited after long term use. Longer follow up, with larger numbers of patients, should determine when, and for how long, tamoxifen can reduce circulating IGF-1.

Effects of two oral contraceptives on plasma levels of insulin-like growth factor I (IGF-I) and growth hormone (hGH)

In 18 healthy women, the effect of two oral contraceptives (OCs) on insulin-like growth factor (IGF-I) and its binding protein-3 (IGFBP-3) and growth hormone (hGH) plasma level were studied before and after intake of either of two OC formulations over 21 days, one containing 2 mg dienogest and 0.03 mg ethinylestradiol (group A) and the other 0.125 mg levonorgestrel and 0.03 mg ethinylestradiol (group B). There was a reduction of the mean IGF-I concentration of 30% (p = 0.008) in the women receiving dienogest-containing pills and 12% (p = 0.006) in women taking the levonogestrel-containing preparation. This difference between drug groups was statistically significant (p = 0.002). A correlation between the control values and the basal-treatment difference (r = 0.945; p = 0.000) was observed only in women of group A. Between basal and treatment cycles the mean plasma levels of hGH remained unchanged in both groups tested, but the 23.5-h integrated mean hGH plasma concentrations (AUC(0-23.5h)) were significantly elevated by 36% (p = 0.016) in comparison to basal values before treatment only in women receiving the levonorgestrel-containing pills. Also, in the women who received the dienogest-containing preparation, the changes of integrated mean plasma level were inversely associated with the control values (r = -0.723; p = 0.025). Neither in group A nor in group B was the mean plasma level of IGFB-3 changed.

IN CONCLUSION

the results of the present analysis indicate that hormonal contraceptives can modulate the GH and IGF-I-axis in the reproductive age. Probably the androgenic progestogen levonorgestrel (0.125 mg/day) opposes the estrogen-induced action. In the women who took the dienogest-containing formulations (anti-androgenic progestogen-group A), the extent of individual changes (hGh and IGF-I) depends on the basal level prior to pill intake. Further studies, especially of long-term intake of OCs, are necessary to confirm these results and to assess the practical relevance for possible effects on connective tissue and bone.

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.

Cyclic changes in serum levels of insulin-like growth factor binding protein-1 in women treated with clomiphene citrate and tamoxifen

In order to investigate the cyclic changes of serum insulin-like growth factor-I (IGF-I), IGF binding protein-1 (IGFBP-1) and IGFBP-3 levels in menstrual cycles treated with or without antiestrogens (clomiphene citrate and tamoxifen), we treated 24 young women having irregular menstrual cycles with either clomiphene citrate (100 mg/day) (n = 12) or tamoxifen (60 mg/day) (n = 12) from the 5th to the 9th day of the menstrual cycle. Without antiestrogens, 12 women with regular menstrual cycles were recruited as controls. There was a preovulatory (day 13) peak of circulating IGFBP-1 in women treated with or without antiestrogens. A significant concomitant increase in serum estradiol was also observed on day 13 of the menstrual cycle in subjects treated with clomiphene citrate and in controls. However, no significant elevation in preovulatory estradiol was detected in women treated with tamoxifen. In clomiphene citrate and control groups, a significant positive correlation was found between circulating IGFBP-1 and estradiol, and between serum levels of IGFBP-1 and inhibin A at the preovulatory stage (on day 13). In contrast, no such association was observed in the tamoxifen group. Unlike cyclic changes in circulating IGFBP-1, serum concentrations of IGF-I and IGFBP-3 remained unchanged throughout the menstrual cycle in all groups. In conclusion, the preovulatory peak of circulating IGFBP-1 can be induced in cycles treated with both clomiphene citrate and tamoxifen. In addition, a significant positive correlation between estradiol, inhibin A and IGFBP-1 at the preovulatory stage indicates that IGFBP-1 may also reflect follicular development and may further be used as an additional indicator to monitor folliculogenesis under clomiphene citrate treatment.