Differential effects of progestins on the circulating IGF-I system

BMI and Contraceptives Affect New Age-, Sex-, and Puberty-adjusted IGF-I and IGFBP-3 Reference Ranges Across Life Span

CONTEXT

Various clinical factors influencing serum levels of insulin-like growth factor I (IGF-I) and its binding protein 3 (IGFBP-3) are not entirely consistently described.

OBJECTIVE

We asked whether body mass index (BMI), contraceptive drugs (CDs), and hormone replacement therapy (HRT) have potential effects on data for interpreting new age-, sex-, and puberty-adjusted reference ranges for IGF-I and IGFBP-3 serum levels.

DESIGN AND SETTING

Subjects were mainly participants from 2 population-based cohort studies: the LIFE Child study of children and adolescents and the LIFE Adult study.

PARTICIPANTS

We investigated 9400 serum samples from more than 7000 healthy and 1278 obese subjects between 3 months and 81 years old.

MAIN OUTCOME MEASURES

Associations between IGF-I or IGFBP-3, measured with a new electrochemiluminescence immunoassay, and the predictors BMI and CDs were estimated using hierarchical linear modeling.

RESULTS

During infancy, obese children had up to 1 SD score (SDS) higher mean predicted IGF-I values, converging with levels of normal-weight subjects up to 13 years old. Between 20 and 40 years of age, obesity was related to up to -0.5 lower IGF-I SDS values than the predicted values. Obesity had less impact on IGFBP-3. Estrogen- and progestin-based CDs, but not HRT, decreased IGF-I and increased IGFBP-3 (P < 0.01) in adolescents (β IGF-I = -0.45, β IGFBP-3  = 0.94) and adults (β IGF-I = -0.43, β IGFBP-3  = 1.12). Conversely, progestin-based CDs were significantly positive associated with IGF-I (β IGF-I  =0.82).

CONCLUSIONS

BMI and CDs must be considered when assessing and interpreting the clinical relevance of IGF-I and IGFBP-3 measurements.

Growth factor genes and change in mammographic density after stopping combined hormone therapy in the California Teachers Study

Background

The contribution of genetic polymorphisms to the large inter-individual variation in mammographic density (MD) changes following starting and stopping use of estrogen and progestin combined therapy (EPT) has not been well-studied. Previous studies have shown that circulating levels of insulin-like growth factors are associated with MD and cross-talk between estrogen signaling and growth factors is necessary for cell proliferation in the breast. We evaluated single nucleotide polymorphisms (SNPs) in growth factor genes in association with MD changes after women stop EPT use.

Methods

We genotyped 191 SNPs in 13 growth factor pathway genes in 284 non-Hispanic white California Teachers Study participants who previously used EPT and collected their mammograms before and after quitting EPT. Percent MD was assessed using a computer-assisted method. Change in percent MD was calculated by subtracting percent MD of an ‘off-EPT’ mammogram from percent MD of an ‘on-EPT’ (i.e. baseline) mammogram. We used multivariable linear regression analysis to investigate the association between SNPs and change in percent MD. We calculated P-values corrected for multiple testing within a gene (P_adj).

Results

Rs1983210 in INHA and rs35539615 in IGFBP1/3 showed the strongest associations. Per minor allele of rs1983210, the absolute change in percent MD after stopping EPT use decreased by 1.80% (a difference in absolute change in percent MD) (P_adj= 0.021). For rs35539615, change in percent MD increased by 1.79% per minor allele (P_adj= 0.042). However, after applying a Bonferroni correction for the number of genes tested, these associations were no longer statistically significant.

Conclusions

Genetic variation in growth factor pathway genes INHA and IGFBP1/3 may predict longitudinal MD change after women quit EPT. The observed differences in EPT-associated changes in percent MD in association with these genetic polymorphisms are modest but may be clinically significant considering that the magnitude of absolute increase in percent MD reported from large clinical trials of EPT ranged from 3% to 7%.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-4981-6) contains supplementary material, which is available to authorized users.

The role of pregnancy, perinatal factors and hormones in maternal cancer risk: a review of the evidence

An understanding of the origin of cancer is critical for cancer prevention and treatment. Complex biological mechanisms promote carcinogenesis, and there is increasing evidence that pregnancy-related exposures influence foetal growth cell division and organ functioning and may have a long-lasting impact on health and disease susceptibility in the mothers and offspring. Nulliparity is an established risk factor for breast, ovarian, endometrial and possibly pancreatic cancer, whilst the risk of kidney cancer is elevated in parous compared with nulliparous women. For breast, endometrial and ovarian cancer, each pregnancy provides an additional risk reduction. The associations of parity with thyroid and colorectal cancers are uncertain. The timing of reproductive events is also recognized to be important. Older age at first birth is associated with an increased risk of breast cancer, and older age at last birth is associated with a reduced risk of endometrial cancer. The risks of breast and endometrial cancers increase with younger age at menarche and older age at menopause. The mechanisms, and hormone profiles, that underlie alterations in maternal cancer risk are not fully understood and may differ by malignancy. Linking health registries and pooling of data in the Nordic countries have provided opportunities to conduct epidemiologic research of pregnancy exposures and subsequent cancer. We review the maternal risk of several malignancies, including those with a well-known hormonal aetiology and those with less established relationships. The tendency for women to have fewer pregnancies and at later ages, together with the age-dependent increase in the incidence of most malignancies, is expected to affect the incidence of pregnancy-associated cancer.

Reproductive history and risk of colorectal adenocarcinoma in parous women: a Nordic population-based case-control study

Background:

Data are conflicting regarding the role of endogenous sex hormones in colorectal carcinogenesis. In this large population-based study, we pooled data from birth and cancer registries in four Nordic countries, to evaluate the risk of colorectal adenocarcinoma in relation to women's reproductive history.

Methods:

We conducted a population-based case–control study among women registered in Nordic birth registries. The study included colorectal adenocarcinoma cases diagnosed in Denmark, Finland, Norway, and Sweden during 1967–2013 and up to 10 matched controls per case, in total 22 185 cases and 220 246 controls. Odds ratios (ORs) with 95% confidence intervals (95% CIs) were derived from conditional logistic regression models. We had limited information available on possible confounders.

Results:

We found no evidence for associations between colorectal adenocarcinoma and parity, age at first and last birth, and time since first and last birth. The risk estimates were also close to unity for specific cancer subsites (proximal and distal colon and rectum). As well, when the analyses were stratified on menopausal status, parity, and mother's year of birth, no indication of associations was found.

Conclusions:

In this large, Nordic population-based study, no evidence for associations was found between women's reproductive history and colorectal adenocarcinoma in parous women.

Nonlinear reduction in risk for colorectal cancer by oral contraceptive use: a meta-analysis of epidemiological studies

PURPOSE

Although the relationship between oral contraceptive (OC) use and colorectal cancer (CRC) risk has been studied extensively, the results of epidemiological studies are controversial. Therefore, we carried out a meta-analysis of epidemiological studies to summarize the available evidence and to quantify the potential dose-response relation.

METHODS

We searched PubMed database for studies of OC use and CRC risk that were published until the end of March 2014. Random- and fixed-effects models were applied to estimate summary relative risks (RRs) and 95 % confidence intervals (CIs).

RESULTS

Twelve cohorts and seventeen case-control studies with a total of 15,790 CRC cases were included in the final analysis. The summary RR for the ever versus never category of OC use was 0.82 (95 % CI 0.76-0.88). Similar result was observed when we compared the longest duration of OC use with the shortest duration (RR = 0.86, 95 % CI 0.76-0.96). Furthermore, the results of stratified analysis were comparable to those of overall meta-analysis. In dose-response analysis, significant inverse associations emerged in nonlinear models for the duration of OC use and CRC (P nonlinearity = 0.001). The greatest risk reduction was observed when the duration of OC use was approximately 42 months. There was moderate heterogeneity in the analysis, and no evidence of small-study bias was observed.

CONCLUSIONS

Based on the findings of this meta-analysis, ever use of OC is associated with lower risk of CRC. Additionally, there is a statistically significant nonlinear inverse association between the duration of OC use and CRC risk.

Adult BMI Change and Risk of Colon Cancer in Postmenopausal Women

Purpose. We recently reported an association of adult BMI change with colon cancer risk. Here, we sought to further explore this association with respect to postmenopausal HRT use in a larger study population. Methods. We included 1,457 postmenopausal women participating in an ongoing population-based case-control study of colon cancer. Results. We confirmed a previously reported association of adulthood weight gain and increased risk of colon cancer: compared to those with <5 kg/m(2) change of BMI, women who reported moderate (5-10 kg/m(2)) and large (>10 kg/m(2)) BMI changes since their 20s had OR estimates of 1.54 (95% CI = 1.09-2.19) and 1.45 (95% CI = 0.90-2.33), respectively (P for trend = 0.05). Stratified analyses showed that this association was limited to HRT nonusers: ORs were 1.77 (95% CI = 1.02-3.05) and 2.21 (95% CI = 1.09-4.45), respectively (P for trend = 0.03), for BMI changes occurring between the 20s decade and time of recruitment among non-users. Similar associations were observed for BMI changes since the 30s decade. There was no association among HRT users. Conclusion. Our results suggest early adulthood weight gain increases colon cancer risk in postmenopausal women who do not use HRT.

Reproductive history and risk of colorectal cancer in postmenopausal women

BACKGROUND

There are conflicting data regarding the role of sex hormones in colorectal cancer development. Whereas clinical trials data indicate that hormone therapy use reduces the risk of colorectal cancer, data from prospective cohort studies suggest that circulating estrogen levels are positively associated with colorectal cancer risk. A surrogate measure of lifetime estrogen exposure is reproductive history. We investigated the relationship between reproductive factors and the risk of colorectal cancer.

METHODS

Subjects were postmenopausal women enrolled in the National Institutes of Health-American Association of Retired Persons Diet and Health Study, a cohort of 214,162 individuals (aged 50-71 years) that included 2014 incident cases of colorectal cancer that occurred over a mean follow-up of 8.2 years. Questionnaires were used to collect data on reproductive factors, including ages at menarche, birth of first child, and menopause; parity, and use of oral contraceptives. Multivariable Cox proportional hazards models were constructed to examine associations between these reproductive factors and the risk of colorectal cancer, with adjustment for established colorectal cancer risk factors. All statistical tests were two-sided.

RESULTS

Age at menopause (≥ 55 vs < 40 years: hazard ratio [HR] = 1.50, 95% confidence interval [CI] = 1.23 to 1.83; P(trend) = .008) and age at birth of first child (≥ 30 vs ≤ 19 years: HR = 1.26, 95% CI = 1.01 to 1.58; P(trend) = .05) were positively associated with the risk of colorectal cancer. Among women with no history of hormone therapy use, age at menarche (≥ 15 vs 11-12 years: HR = 0.73, 95% CI = 0.57 to 0.94; P(trend) = .02) and parity (≥ 5 children vs no children: HR = 0.80, 95% CI = 0.63 to 1.02; P(trend) = .10) were inversely associated with the risk of colorectal cancer.

CONCLUSION

These data support a role for sex hormones in colorectal tumorigenesis and suggest that greater endogenous estrogen exposure may increase the risk of colorectal cancer in postmenopausal women.

Determinants of IGF1 and GH across the weight spectrum: from anorexia nervosa to obesity

CONTEXT

Chronic starvation is characterized by GH resistance, and obesity is characterized by decreased GH secretion. In both extremes, IGF1 levels may be low and androgen levels may be abnormal.

OBJECTIVE

To investigate the determinants of IGF1 and GH across the weight spectrum in women.

DESIGN

Cross-sectional study.

SETTING

Clinical research center.

STUDY PARTICIPANTS

In total, 32 women had participated in the study: 11 women with anorexia nervosa (AN), 11 normal-weight women, and 10 obese women of comparable mean age.

INTERVENTION

None.

MAIN OUTCOME MEASURES

Pooled hourly overnight serum samples assayed for IGF1, GH, estradiol (E(2)), testosterone, SHBG, insulin, free fatty acids, and trunk fat.

RESULTS

Free testosterone was higher in obese women and lower in women with AN than in normal-weight women, and was the only independent (and positive) predictor of IGF1 levels, accounting for 14% of the variability (P=0.032) in the group as a whole. This relationship was stronger when obese women were excluded, with free testosterone accounting for 36% of the variability (P=0.003). Trunk fat accounted for 49% of the variability (P<0.0001) of GH, with an additional 7% of the variability attributable to E(2) (P=0.042) in the group as a whole, but was not a significant determinant of GH secretion when obese women were excluded.

CONCLUSIONS

Free testosterone is a significant determinant of IGF1 levels in women across the body weight spectrum. In contrast, GH secretion is differentially regulated at the extremes of the weight spectrum.

Postmenopausal estrogen and progestin effects on the serum proteome

Background

Women's Health Initiative randomized trials of postmenopausal hormone therapy reported intervention effects on several clinical outcomes, with some important differences between estrogen alone and estrogen plus progestin. The biologic mechanisms underlying these effects, and these differences, have yet to be fully elucidated.

Methods

Baseline serum samples were compared with samples drawn 1 year later for 50 women assigned to active hormone therapy in both the estrogen-plus-progestin and estrogen-alone randomized trials, by applying an in-depth proteomic discovery platform to serum pools from 10 women per pool.

Results

In total, 378 proteins were quantified in two or more of the 10 pooled serum comparisons, by using strict identification criteria. Of these, 169 (44.7%) showed evidence (nominal P < 0.05) of change in concentration between baseline and 1 year for one or both of estrogen-plus-progestin and estrogen-alone groups. Quantitative changes were highly correlated between the two hormone-therapy preparations. A total of 98 proteins had false discovery rates < 0.05 for change with estrogen plus progestin, compared with 94 for estrogen alone. Of these, 84 had false discovery rates <0.05 for both preparations. The observed changes included multiple proteins relevant to coagulation, inflammation, immune response, metabolism, cell adhesion, growth factors, and osteogenesis. Evidence of differential changes also was noted between the hormone preparations, with the strongest evidence in growth factor and inflammation pathways.

Conclusions

Serum proteomic analyses yielded a large number of proteins similarly affected by estrogen plus progestin and by estrogen alone and identified some proteins and pathways that appear to be differentially affected between the two hormone preparations; this may explain their distinct clinical effects.

Progestagen component in combined hormone replacement therapy in postmenopausal women and breast cancer risk: a debated clinical issue

The relevance of the progestagen component in combined hormone replacement therapy (HRT) for breast cancer risk has been long debated. In vitro studies have shown that progestins exert both genomic transcriptional and non-genomic effects that can enhance the proliferation, invasiveness and spread of breast cancer cells. According to a novel hypothesis, progestins can still activate cancer stem cells in patients with pre-existing, clinically undetected breast cancer. However, some experimental and clinical data suggest that different progestins may have a different impact on the pathophysiology of malignant breast cells. In vitro studies on estrogen receptor (ER)+ breast cancer cells have shown that the addition of medroxyprogesterone acetate (MPA) to estradiol (E(2)) produces a significantly higher increase of the mRNA levels and activities of estrogen-activating enzymes aromatase, 17beta hydroxysteroid dehydrogenase type-1 and sulfatase when compared with progesterone plus E(2). In randomised trial performed on ovariectomised adult female monkeys, oral E(2) plus MPA have resulted in a significantly greater proliferation of breast lobular and ductal epithelium when compared with placebo, whereas E(2) plus micronised progesterone have not. In the same experimental model, oral E(2) plus MPA have been found to induce the expression of genes encoding epidermal growth factor receptor (EGFR) ligands and downstream targets, whereas E(2) alone or E(2) plus micronised progesterone had no or modest effects on EGFR-related genes. In last years, some clinical studies on HRT users have shown that androgenic progestin- or MPA-based formulations are associated with an increased breast cancer incidence, whereas micronised progesterone- or dydrogesterone-based formulations are not. Further basic and clinical investigations on this topic are strongly warranted to elucidate whether the choice of the progestagen component in combined HRT could be of clinical relevance as for breast cancer risk.

Insulin, insulin-like growth factor-I, and risk of breast cancer in postmenopausal women

BACKGROUND

The positive association between obesity and postmenopausal breast cancer has been attributed, in part, to the fact that estrogen, a risk factor for breast cancer, is synthesized in adipose tissue. Obesity is also associated with high levels of insulin, a known mitogen. However, no prospective studies have directly assessed associations between circulating levels of insulin and/or insulin-like growth factor (IGF)-I, a related hormone, and the risk of breast cancer independent of estrogen level.

METHODS

We conducted a case-cohort study of incident breast cancer among nondiabetic women who were enrolled in the Women's Health Initiative Observational Study (WHI-OS), a prospective cohort of 93,676 postmenopausal women. Fasting serum samples obtained at study entry from 835 incident breast cancer case subjects and from a subcohort of 816 randomly chosen WHI-OS subjects were tested for levels of insulin, glucose, total IGF-I, free IGF-I, insulin-like growth factor binding protein-3, and estradiol. Multivariable Cox proportional hazards models were used to estimate associations between levels of the serologic factors and baseline characteristics (including body mass index [BMI]) and the risk of breast cancer. All statistical tests were two-sided. Results Insulin levels were positively associated with the risk of breast cancer (hazard ratio [HR] for highest vs lowest quartile of insulin level = 1.46, 95% confidence interval [CI] = 1.00 to 2.13, P(trend) = .02); however, the association with insulin level varied by hormone therapy (HT) use (P(interaction) = .01). In a model that controlled for multiple breast cancer risk factors including estradiol, insulin level was associated with breast cancer only among nonusers of HT (HR for highest vs lowest quartile of insulin level = 2.40, 95% CI = 1.30 to 4.41, P(trend) < .001). Obesity (BMI >or=30 kg/m(2)) was also associated with the risk of breast cancer among nonusers of HT (HR for BMI >or=30 kg/m(2) vs 18.5 to <25 kg/m(2) = 2.12, 95% CI = 1.26 to 3.58, P(trend) = .003); however, this association was attenuated by adjustment for insulin (P(trend) = .40).

CONCLUSION

These data suggest that hyperinsulinemia is an independent risk factor for breast cancer and may have a substantial role in explaining the obesity-breast cancer relationship.

Insulin resistance, obesity and breast cancer risk

Breast cancer (BC) is one of the most important problems of public health. Among the avoidable risk factors during a woman's life, overweight and obesity are very important ones. Furthermore they are increasing worldwide. The risk of breast cancer is traditionally linked to obesity in postmenopausal women; conversely, it is neutral or even protective in premenopausal women. Since the initiator and promoter factors for BC act over a long time, it seems unlikely that the menopausal transition may have too big an impact on the role of obesity in the magnitude of the risk. We reviewed the literature in an attempt to understand this paradox, with particular attention to the body fat distribution and its impact on insulin resistance. The association of insulin resistance and obesity with BC risk are biologically plausible and consistent. Estradiol (E2) and IGFs act as mitogens in breast cancer cells. They act together and reciprocally. However the clinical and biological methods to assess the impact of insulin resistance are not always accurate. Furthermore insulin resistance is far from being a constant feature in obesity, particularly in premenopausal women; this complicates the analysis and explains the discrepancies in large prospective trials. The most consistent clinical feature to assess risk across epidemiological studies seems to be weight gain during lifetime. Loss of weight is associated with a lower risk for postmenopausal BC compared with weight maintenance. This observation should be an encouragement for women since loss of weight may be an effective strategy for breast cancer risk reduction.

24-hour serum levels of growth hormone, prolactin, and cortisol in pre- and postmenopausal women: the effect of combined estrogen and progestin treatment

OBJECTIVE

Our objective was to study the 24-h profiles of GH, prolactin (PRL), and cortisol concentrations in older postmenopausal and middle-aged premenopausal women, before and after estrogen-progestin treatment (EPT).

DESIGN

The study was a randomized, placebo-controlled, double-blind trial. GH, PRL, and cortisol were sampled every 20 min for 24 h in 18 postmenopausal (aged 58-70 yr) and 17 premenopausal (aged 45-51 yr) women before and after 6 months of EPT.

RESULTS

The mean 24-h GH (1.0 vs. 1.8 mU/liter, P = 0.033) and PRL (6.8 vs. 10.0 ng/ml, P = 0.009) concentrations were lower in postmenopausal than in premenopausal women. After EPT, the postmenopausal GH and PRL did not differ from premenopausal baseline levels. Postmenopausal mean 24-h GH (P < 0.001) and PRL (P = 0.002), daytime GH (P < 0.001) and nighttime PRL (P = 0.004) were higher during EPT compared with placebo. Cortisol levels did not differ. Premenopausal mean nighttime PRL (P = 0.026) and cortisol (P = 0.018) were higher during EPT compared with placebo. Postmenopausal PRL and premenopausal GH and PRL concentrations were higher at night than during the day. EPT did not alter this pattern.

CONCLUSIONS

Menopause was associated with decreased 24-h levels of GH and PRL, which were reversible with EPT. In contrast, cortisol levels were not affected by menopause or EPT. In middle-aged premenopausal women, the studied effects of EPT were limited to nighttime increases of PRL and cortisol.

Insulin, insulin-like growth factor-I, endogenous estradiol, and risk of colorectal cancer in postmenopausal women

Obesity is a risk factor for colorectal cancer, and hyperinsulinemia, a common condition in obese patients, may underlie this relationship. Insulin, in addition to its metabolic effects, has promitotic and antiapoptotic activity that may be tumorigenic. Insulin-like growth factor (IGF)-I, a related hormone, shares sequence homology with insulin, and has even stronger mitogenic effects. However, few prospective colorectal cancer studies directly measured fasting insulin, and none evaluated free IGF-I, or endogenous estradiol, a potential cofactor in postmenopausal women. Therefore, we conducted a case-cohort investigation of colorectal cancer among nondiabetic subjects enrolled in the Women's Health Initiative Observational Study, a prospective cohort of 93,676 postmenopausal women. Fasting baseline serum specimens from all incident colorectal cancer cases (n = 438) and a random subcohort (n = 816) of Women's Health Initiative Observational Study subjects were tested for insulin, glucose, total IGF-I, free IGF-I, IGF binding protein-3, and estradiol. Comparing extreme quartiles, insulin [hazard ratio (HR)(q4-q1), 1.73; 95% confidence interval (CI), 1.16-2.57; P(trend) = 0.005], waist circumference (HR(q4-q1), 1.82; 95% CI, 1.22-2.70; P(trend) = 0.001), and free IGF-I (HR(q4-q1), 1.35; 95% CI, 0.92-1.98; P(trend) = 0.05) were each associated with colorectal cancer incidence in multivariate models. However, these associations each became nonsignificant when adjusted for one another. Endogenous estradiol levels, in contrast, were positively associated with risk of colorectal cancer (HR comparing high versus low levels, 1.53; 95% CI, 1.05-2.22), even after control for insulin, free IGF-I, and waist circumference. These data suggest the existence of at least two independent biological pathways that are related to colorectal cancer: one that involves endogenous estradiol, and a second pathway broadly associated with obesity, hyperinsulinemia, and free IGF-I.

Hyper-insulinaemia and cancer, meta-analyses of epidemiological studies

BACKGROUND

A substantial body of evidence links sex hormones, diet, excess body weight and physical activity to the risk of developing cancer at several sites common in affluent countries. The hypothesis that high circulating levels of insulin could be the underlying factor increasing cancer risk has been proposed. Epidemiological studies on markers of hyper-insulinaemia and cancer are reviewed and summarized.

METHODS

Studies of cancers of the colon and rectum, pancreas, breast, and endometrium examining the association with blood levels of C-peptide, insulin, glucose, glycated haemoglobin (HbA1c) were searched in PubMed. Multivariate, adjusted relative risks (RR) and their 95% confidence intervals were abstracted and summarized by meta-analyses.

RESULTS

Most of the studies identified were cohorts that relied on measurements obtained at baseline or assessed in blood stored at low temperature several years before the onset of cancer. The meta-analyses showed excess risks of colorectal and pancreatic cancers associated with higher levels of circulating C-peptide/insulin and with markers of glycaemia. Significant heterogeneity was found among four epidemiological studies of endometrial cancer and C-peptide giving a summary RR compatible with no association. Overall breast cancer risk was significantly higher in the upper categories of C-peptide/insulin, however, the excess derived entirely from retrospective studies.

CONCLUSION

Current evidence suggests that subjects who develop colorectal and pancreatic cancers have increased pre-diagnostic blood levels of insulin and glucose.

Differential effects of various progestogens on metabolic risk factors for breast cancer

Biological and epidemiological findings suggest that metabolic factors - insulin, insulin-like growth factor-I (IGF-I) and sex hormone-binding globulin (SHBG) - are involved in the development and promotion of breast cancer. Estrogens, particularly if administered orally, counteract metabolic factors that increase breast cancer risk, i.e. they reduce insulin and IGF-I and increase SHBG. This could contribute toward explaining epidemiological data showing that unopposed oral estrogens do not increase breast cancer risk, or do so only modestly. In contrast to natural progesterone and progesterone-derived progestins, progestins endowed with androgenic (or glucocorticoid) activity negatively influence these metabolic factors, counteracting the favorable effects of estrogens. While most biological and epidemiological findings suggest that natural progesterone does not augment breast cancer risk, available data show an increased risk with synthetic progestins - with the possible exception of progesterone-derived dydrogesterone. Different mechanisms for different progestins could possibly be involved. Differences from progesterone with regard to pharmacokinetics and pharmacodynamics, potency, interaction with the two isoforms of the progesterone receptor, and binding to other steroid receptors could all be relevant. These remain theoretical speculations for the time being, but the possibility that some progestins increase breast cancer risk through their negative influence on metabolic factors cannot be rejected.

The effects of sex steroid replacement therapy on an expanded panel of IGF-related peptides

BACKGROUND

Oral estrogen alone (EA) decreases concentrations of total IGF-I while increasing IGFBP-1, but data on other IGF-related peptides are inconsistent and/or sparse. Combined oral estrogen and progestin (EP) may have differential effects on IGF-related peptides dependent on its progestin-associated androgenic activity. The aim of this study was to clarify these relationships, as circulating IGF-related peptides are potential surrogates of predisposition to common chronic diseases.

DESIGN

Using an open-labelled cross-sectional design within a bowel cancer screening trial (aged 55-64 years), we determined total IGF-I, IGF-II, IGFBP-2 and IGFBP-3 in fasted serum from 210 healthy women and free IGF-I (by ultrafiltration), insulin, IGFBP-1 and IGFBP-1:IGF-I binary complex in a selected subset of 92 women. Unadjusted and adjusted (using generalized linear models) means were compared.

RESULTS

Among EA users, mean concentrations for total IGF-I (adjusted P=0.004) and free IGF-I (P<0.001) were reduced, whereas mean concentrations of IGFBP-1 (P=0.001) and binary complex (P=0.01) were increased compared with non-users. Taken as a whole group, EP use was not associated with differences in concentrations of IGF-related peptides, but on sub-group analyses, mean concentrations associated with the use of progestins with reduced androgenic activity reflected the use of EA. By contrast, mean IGFBP-2 concentrations were significantly reduced among both EA (P=0.008) and EP (P=0.002) users, irrespective of androgenic activity. Neither EA nor EP influenced mean concentrations of IGF-II, insulin and IGFBP-3.

CONCLUSIONS

The uses of oral sex steroid replacements are associated with significant changes in several IGF-related analytes in a preparation-specific manner, suggesting different regulatory mechanisms. However, the directions of these changes do not fit simple correlative models of predisposition to common diseases.

Estro-progestin supplementation enhances the growth hormone secretory responsiveness to ghrelin infusion in postmenopausal women

OBJECTIVE

To assess the effects of estro-progestin supplementation on ghrelin-mediated GH release, we studied the consequence of ghrelin or saline injection before and after 60 days of hormone therapy or placebo administration in postmenopausal subjects.

DESIGN

A prospective double blind, placebo-controlled, and parallel cohort study.

SETTING

Catholic University of Sacred Heart, Operative Division of Endocrinological Gynecology.

PATIENT(S)

Eighteen postmenopausal women participated in the study.

INTERVENTION(S)

Ten women were randomized to receive estro-progestin treatment (2 mg of hemihydrate E(2) and 10 mg of dydrogesterone in a continuous sequential regimen); eight women were treated with placebo. All patients underwent in a randomized order a ghrelin test (1 microg/kg IV bolus) or a saline infusion (2-mL IV bolus) on two different days, before and after 60 days of treatment.

MAIN OUTCOME MEASURE(S)

Basal hormonal assays, including ghrelin basal levels. The GH levels were measured at baseline and after 15, 30, 60, 90 minutes of ghrelin or saline injection.

RESULT(S)

The acute ghrelin injection released a notable GH secretion in all postmenopausal women. After estro-progestin therapy the ghrelin-stimulated GH response was significantly higher than before treatment. In particular, the percent increase of ghrelin GH-releasing effect, expressed as incremental area under the curve (AUCi-GH) was more than 50% after hormone therapy.

CONCLUSION(S)

In postmenopausal women estro-progestin treatment clearly influenced the ghrelin-stimulated GH secretion.

Physical activity and colon cancer risk among women in the California Teachers Study

BACKGROUND

Existing data suggest that physical activity reduces colon cancer risk, but the association is not consistently observed in women. One potential explanation for this inconsistency is that hormone therapy, which is associated with lower colon cancer risk, acts as a modifier of the physical activity/colon cancer relationship.

METHODS

Participants in the California Teachers Study (N = 120,147), a prospective cohort of female teachers and administrators residing in California, ages 22 to 84 years at baseline and with no prior history of colon cancer were eligible for study. Between 1996 and 2002, 395 patients were diagnosed with invasive colon cancer. The relative risks (RR) associated with lifetime (high school through age 54 years or current age) and recent (past 3 years) strenuous and moderate recreational physical activity were estimated using Cox proportional hazards regression models.

RESULTS

Combined lifetime moderate and strenuous recreational physical activity was only modestly associated with colon cancer risk in the cohort [>or=4 versus <or=0.5 h/wk/y: RR, 0.75; 95% confidence interval, 0.57-1.00; P(trend) = 0.23]. Lifetime physical activity reduced colon cancer risk among postmenopausal women who had never taken hormone therapy (>or=4 versus <or=0.5 h/wk/y: RR, 0.51; 95% confidence interval, 0.31-0.85; P(trend) = 0.02). Postmenopausal women with histories of hormone therapy use had lower colon cancer risk, but their risk was not associated with physical activity. The likelihood ratio test for interaction between hormone use and lifetime moderate plus strenuous physical activity was of borderline statistical significance (P = 0.05). We observed no effect modification by age, body mass index, smoking status, menopausal status, or folate intake.

CONCLUSIONS

Lifetime recreational physical activity may protect against colon cancer among postmenopausal women who have never used hormone therapy. Among hormone therapy users, who have lower risk of colon cancer, recreational physical activity does not seem to provide any additional benefit. With declining rates of hormone therapy use, physical activity offers one possible means for reducing women's colon cancer risk.

Effects of the route of oestrogen administration on IGF-1 and IGFBP-3 in healthy postmenopausal women: results from a randomized placebo-controlled study

OBJECTIVE

Oestrogens can modulate the action or secretion of GH. Previous studies in postmenopausal women have shown a differential effect between transdermal 17beta-oestradiol and oral ethynyl-oestradiol on GH and IGF-1 concentrations. This secondary analysis, based on a large randomized trial, aimed to estimate the effect of the route of administration of 17beta-oestradiol in combined hormone replacement therapy with progesterone on IGF-1 and IGFBP-3 levels.

DESIGN

IGF-1 and IGFBP-3 were evaluated in a randomized study of 196 healthy postmenopausal women who were randomly allocated to receive on a continuous basis either 1 mg of 17beta-oestradiol orally combined with a daily intake of 100 mg progesterone (group 1; n = 63), or 50 microg of 17beta-oestradiol transdermally combined with a daily intake of 100 mg progesterone (group 2; n = 68), or triple dummy placebo (group 3; n = 65) over a 6-month period. IGF1 and IGFBP-3 levels were available for 133 women.

RESULTS

Oral oestrogen significantly decreased IGF-1 levels compared to placebo (P = 0.04) and transdermal oestrogen (P = 0.004), whereas transdermal oestrogen had no effect on IGF-1 levels compared to placebo (P = 0.56). As regards IGFBP-3, no significant difference was detected between the three groups.

CONCLUSIONS

Our data indicate that the route of oestrogen administration can influence IGF-1 levels. IGF-1 concentrations decreased significantly with oral oestrogen, whereas no significant change was observed with transdermal oestrogen at 6 months. The clinical relevance of these differential effects remains to be determined, particularly with regard to the risk for cardiovascular diseases.

Estrogenic effects of marijuana smoke condensate and cannabinoid compounds

Chronic exposure to marijuana produces adverse effects on the endocrine and reproductive systems in humans; however, the experimental evidence for this presented thus far has not been without controversy. In this study, the estrogenic effect of marijuana smoke condensate (MSC) was evaluated using in vitro bioassays, viz., the cell proliferation assay, the reporter gene assay, and the ER competitive binding assay. The results of these assays were compared with those of three major cannabinoids, i.e., THC, CBD, and CBN. The estrogenic effect of MSC was further confirmed by the immature female rat uterotrophic assay. MSC stimulated the estrogenicity related to the ER-mediated pathway, while neither THC, CBD, nor CBN did. Moreover, treatment with 10 and 25 mg/kg MSC induced significant uterine response, and 10 mg/kg MSC resulted in an obvious change in the uterine epithelial cell appearance. MSC also enhanced the IGFBP-1 gene expression in a dose-dependent manner. To identify the constituents of MSC responsible for its estrogenicity, the MSC fractionated samples were examined using another cell proliferation assay, and the estrogenic active fraction was analyzed using GC-MS. In the organic acid fraction that showed the strongest estrogenic activity among the seven fractions of MSC, phenols were identified. Our results suggest that marijuana abuse is considered an endocrine-disrupting factor. Furthermore, these results suggest that the phenolic compounds contained in MSC play a role in its estrogenic effect.

Pregnancy, progesterone and progestins in relation to breast cancer risk

In the last two decades the prevailing opinion, supported by the "estrogen augmented by progesterone" hypothesis, has been that progesterone contributes to the development of breast cancer (BC). Support for this opinion was provided by the finding that some synthetic progestins, when added to estrogen in hormone replacement therapy (HRT) for menopausal complaints, increase the BC risk more than estrogen alone. However, recent findings suggest that both the production of progesterone during pregnancy and the progesterone endogenously produced or exogenously administered outside pregnancy, does not increase BC risk, and could even be protective. The increased BC risk found with the addition of synthetic progestins to estrogen in HRT seems in all likelihood due to the fact that these progestins (medroxyprogesterone acetate and 19-nortestosterone-derivatives) are endowed with some non-progesterone-like effects which can potentiate the proliferative action of estrogens. The use of progestational agents in pregnancy, for example to prevent preterm birth, does not cause concern in relation to BC risk.

Progestins and progesterone in hormone replacement therapy and the risk of breast cancer

Controlled studies and most observational studies published over the last 5 years suggest that the addition of synthetic progestins to estrogen in hormone replacement therapy (HRT), particularly in continuous-combined regimen, increases the breast cancer (BC) risk compared to estrogen alone. By contrast, a recent study suggests that the addition of natural progesterone in cyclic regimens does not affect BC risk. This finding is consistent with in vivo data suggesting that progesterone does not have a detrimental effect on breast tissue. The increased BC risk found with the addition of synthetic progestins to estrogen could be due to the regimen and/or the kind of progestin used. Continuous-combined regimen inhibits the sloughing of mammary epithelium that occurs after progesterone withdrawal in a cyclic regimen. More importantly, the progestins used (medroxyprogesterone acetate and 19-Nortestosterone-derivatives) are endowed with some non-progesterone-like effects, which can potentiate the proliferative action of estrogens. Particularly relevant seem to be the metabolic and hepatocellular effects (decreased insulin sensitivity, increased levels and activity of insulin-like growth factor-I, and decreased levels of SHBG), which contrast the opposite effects induced by oral estrogen.