Effects of oral versus transdermal estrogen on the growth hormone/insulin-like growth factor I axis in younger and older postmenopausal women: a clinical research center study

Modulating Effects of Progesterone on Spontaneous Nocturnal and Ghrelin-Induced GH Secretion in Postmenopausal Women

BACKGROUND

Oral administration of estradiol (E2) generally increases GH secretion in postmenopausal women. Oral administration of E2 is associated with a decrease in IGF-1, whereas parenteral or transdermally administered E2 may have no effect on GH. The effect of progesterone (P4) on GH secretion has rarely been studied. We hypothesized that moderately increased serum E2 levels stimulate GH and that P4 modulates E2-stimulated GH secretion.

STUDY DESIGN

Four parallel groups of randomly assigned postmenopausal women (n = 40). Treatments were saline placebo and oral placebo, saline placebo and oral micronized P4 (3 × 200 mg/d IM), E2 (5 mg IM) and oral placebo, and E2 IM and oral micronized P4. Outcome measures were overnight GH secretion (10 hours), stimulated (ghrelin, 0.3 µg/kg IV bolus) GH secretion, and CT-estimated visceral fat.

RESULTS

Intramuscular E2 administration did not alter nocturnal and ghrelin-stimulated GH secretion. Nocturnal GH secretion was not changed by P4 administration. However, P4 diminished ghrelin-stimulated pulsatile GH release with or without E2 (average, 7.20 ± 2.14 and 9.58 ± 1.97 µg/L/2 h, respectively; P = 0.045). Respective outcomes for mean GH concentrations and GH peak amplitudes were 0.97 ± 0.31 and 1.52 μg/L ± 0.29 (P = 0.025) and 2.76 ± 1.04 and 3.95 μg/L ± 0.90 (P = 0.031). Ghrelin-stimulated GH secretion correlated negatively with P4 concentration with or without correction for visceral fat area in the regression equation (R = 0.49, P = 0.04, β = -0.040 ± 0.016).

CONCLUSIONS

Low-range physiological E2 concentrations do not affect spontaneous or ghrelin-stimulated pulsatile GH secretion. Conversely, P4 inhibits ghrelin-stimulated GH secretion in a concentration-dependent fashion. The mechanistic aspects and physiological significance of natural P4's regulation of ghrelin-evoked GH secretion require further study.

Effects of Toremifene, a Selective Estrogen Receptor Modulator, on Spontaneous and Stimulated GH Secretion, IGF-I, and IGF-Binding Proteins in Healthy Elderly Subjects

Context:

Estrogens amplify spontaneous and stimulated growth hormone (GH) secretion, whereas they diminish GH-dependent insulin-like growth factor (IGF)-I in a dose-dependent manner. Selective estrogen receptor modulators (SERMs), including tamoxifen and toremifene, are widely adjunctively used in breast and prostate cancer. Although some endocrine effects of tamoxifen are known, few data are available for toremifene.

Objective:

To explore sex-dependent effects of toremifene on spontaneous 10-hour overnight GH secretion, followed by GH-releasing hormone–ghrelin stimulation. Additionally, effects on IGF-I, its binding proteins, and sex hormone–binding globulin (SHBG) were quantified.

Participants and Design:

Twenty men and 20 women, within an allowable age range of 50 to 80 years, volunteered for this double-blind, placebo-controlled prospective crossover study. Ten-minute blood sampling was done for 10 hours overnight and then for 2 hours after combined GH-releasing hormone–ghrelin injection.

Main Outcome Measures:

Pulsatile GH and stimulated GH secretion, and fasting levels of IGF-I, IGF-binding protein (IGFBP)1, IGFBP3, and SHBG.

Results:

Toremifene did not enhance pulsatile or stimulated GH secretion, but decreased IGF-I by 20% in men and women. IGFBP3 was unchanged, whereas while IGFBP1 and SHBG increased in both sexes to a similar extent.

Conclusions:

The expected rise in spontaneous and stimulated GH secretion under the diminished negative feedback restraint of powered IGF-I favors a central inhibitory antiestrogenic effect of toremifene. Estrogenic effects of toremifene on the liver were present, as evidenced by increased IGFBP1 and SHBG levels. Men and women responded to this SERM comparably.

Hormone and genetic study in male to female transsexual patients

BACKGROUND

Data of the literature demonstrated controversial results of a correlation between transsexualism and genetic mutations.

AIM

To evaluate the hormone and gene profile of male-female (M-F) transsexual.

SUBJECTS AND METHODS

Thirty M-F transsexuals aged 24-39. Seventeen had already undergone sex reassignment surgery, 13 were awaiting. All subjects had been undergoing estrogen and antiandrogen therapy. We studied hormones of the hypothalamus- pituitary-testicular axis, thyroid and adrenal profile, GH basal and after GHRH stimulation, IGF-I. The gene study analyzed SRY, AR, DAX1, SOX9, AZF region of the Y chromosome.

RESULTS

Pre-surgery subjects had elevated PRL, reduced testosterone and gonadotropins. Post-surgery subjects showed reduced androgens, a marked increase in LH and FSH and normal PRL. Cortisol and ACTH were similar to reference values in pre- and post-surgery patients. There was a marked increase in the baseline and post-stimulation GH values in 6 of the 13 pre-surgery patients, peaking at T15. IGF-I was similar to reference values in both groups except for one post-surgery patient, whose level was below the normal range. There were no polymorphisms in the amplified gene region for SOX9, and a single nucleotide synonimous polymorphism for DAX1. No statistically significant differences were seen in the mean of CAG repeats between controls and transsexual subjects. SRY gene was present in all subjects. Qualitative analysis of the AZFa, AZFb, and AZFc regions did not reveal any microdeletions in any subject.

CONCLUSIONS

This gender disorder does not seem to be associated with any molecular mutations of some of the main genes involved in sexual differentiation.

Insulin-like growth factor 1 and musculoskeletal pain among breast cancer patients on aromatase inhibitor therapy and women without a history of cancer

PURPOSE

Musculoskeletal pain is a common side effect of aromatase inhibitors (AIs), the adjuvant hormonal treatment of choice for postmenopausal estrogen-receptor-positive breast cancer. Although the pain is usually attributed to the estrogen depletion associated with AIs, not all women on AIs experience these symptoms. Thus, the goal of this study was to examine whether changes in the insulin-like growth factor (IGF) axis were associated with pain among women initiating AI therapy or a comparison group of women without a history of cancer.

METHODS

Data were analyzed from a cohort study of 52 breast cancer patients for whom AI therapy was planned and 88 women without a history of cancer. Questionnaire data on pain symptoms were collected, and blood was drawn at baseline (prior to AI therapy for patients) and 6 months after baseline. The blood samples were assayed for IGF-1 and IGF-binding protein-3 (IGFBP-3).

RESULTS

While results showed no statistically significant changes in any of the measures across time for either the breast cancer or the comparison group, increases in both IGF-1 concentrations and the IGF-1/IGFBP-3 ratio over the first 6 months of AI treatment were significantly associated with the onset or increase in musculoskeletal pain among the breast cancer patients. Associations between IGF-1, IGFBP-3, and the IGF-1/IGFBP-3 ratio and pain were not observed in the comparison group.

CONCLUSIONS

Although preliminary, findings from this study implicate the IGF axis in the development of AI-associated musculoskeletal pain and represent a first step in developing effective interventions to alleviate this side effect.

Insulinlike growth factor-1, insulinlike growth factor binding protein-1, and cognitive function in older men and women

OBJECTIVES

To assess the association between insulinlike growth factor (IGF)-1 and IGF binding protein (IGFBP)-1 with three cognitive function tests in a healthy elderly population.

DESIGN

Cross-sectional analyses from the Rancho Bernardo Cohort Study.

SETTING

Southern California community of Rancho Bernardo.

PARTICIPANTS

Men (n=636) and women (n=899) from the Rancho Bernardo study (median age 74) were assessed between 1988 and 1992 for cognitive function using the Mini-Mental State Examination (MMSE), Verbal Fluency (VF) test, and Trail-Making Test Part B (Trails B). Blood samples were obtained at the same time for IGF-1 and IGFBP-1 levels. The association between biomarkers and cognitive function tests was assessed by dichotomizing tests at the clinically relevant cutoff using logistic regression and according to tertiles and continuous IGF-1 and IGFBP-1 levels using multivariate linear regression analyses.

RESULTS

The mean MMSE, VF and Trails B scores indicated better cognitive function with higher IGF-1 tertile. Multivariate analyses showed that VF and MMSE were each significantly associated with IGF-1 in a dose-response manner for men (P for trend=.001), but no cognitive function tests were related to IGF-1 in women. For men, the highest IGFBP-1 tertile was inversely and significantly different from the lowest tertile for the MMSE test only (P for trend=.02).

CONCLUSION

IGF-1 was independently and positively related to MMSE and VF in men, and IGFBP-1 was inversely associated with MMSE in men. Sex differences in the association should be further investigated.

Androgens may mediate a relative preservation of IGF-I levels in overweight and obese women despite reduced growth hormone secretion

CONTEXT

Obesity is characterized by reduced GH secretion, but data regarding IGF-I levels and their determinants are conflicting.

OBJECTIVES

The objectives were to determine whether IGF-I levels are reduced and to investigate determinants of GH and IGF-I in healthy overweight and obese women.

DESIGN

A cross-sectional study was performed.

SETTING

The study was conducted at a General Clinical Research Center.

STUDY PARTICIPANTS

Thirty-four healthy women without pituitary/hypothalamic disease participated, including 11 lean [body mass index (BMI) <25 kg/m(2)], 12 overweight (BMI > or =25 kg/m(2) and <30 kg/m(2)), and 11 obese (BMI > or =30 kg/m(2)) women of comparable age (overall mean age, 30.7 +/- 7.8 yr).

INTERVENTION

There was no intervention.

MAIN OUTCOME MEASURES

The main outcome measures were frequent sampling (every 10 min for 24 h) for GH, peak GH after GHRH-arginine stimulation, IGF-I, IGF binding protein-3, estrone, estradiol, testosterone, free testosterone, SHBG, homeostasis model assessment of insulin resistance, and abdominal fat.

RESULTS

Mean 24-h GH and peak stimulated GH were lower in overweight than lean women and lowest in obese women. Mean IGF-I levels trended lower in obese, but not overweight, compared with lean women. Free testosterone was positively associated with IGF-I (R = 0.36, P = 0.04) but not with GH measures. Visceral fat was the only determinant of mean 24-h GH (R(2) = 0.66, P < 0.0001) and of peak stimulated GH (R(2) = 0.63, P < 0.0001), and mean 24-h GH accounted for 39% of the variability of IGF-I (P = 0.0002), with an additional 28% (P < 0.0001) attributable to free testosterone levels.

CONCLUSIONS

Despite a linear decrease in GH secretion and peak stimulated GH levels with increasing BMI in healthy overweight and obese women, IGF-I levels were not commensurately reduced. Androgens may contribute to this relative preservation of IGF-I secretion in overweight and obese women despite reduced GH secretion.

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.

IGF1 CA repeat polymorphisms, lifestyle factors and breast cancer risk in the Long Island Breast Cancer Study Project

Insulin-like growth factor I (IGF-I) is an important regulator of growth and differentiation and is a potent mitogen for human breast cancer cells. Recent investigations suggest an association between cytosine-adenine dinucleotide (CA)n repeat polymorphisms of the IGF1 gene and IGF-I levels and further evidence indicates that genotype may influence breast cancer risk. We assessed the relation between IGF1 (CA)n repeats and breast cancer, and evaluated modification of genotype effects according to traditional breast cancer risk factors in 1028 breast cancer cases and 1086 controls. An increased risk of breast cancer was seen for genotypes that included alleles with fewer than (CA)19 repeats when compared to (CA)19 repeat carriers, an association that was particularly strong among premenopausal women [odds ratio (OR)=3.31; 95% confidence interval (CI)=1.47, 7.48]. No significant association was observed between an IGF1 genotype with no (CA)19 repeat compared to (CA)19 repeat genotypes in either pre- or postmenopausal women overall. However, when traditional breast cancer risk factors were considered, premenopausal women with genotypes that lacked a (CA)19 repeat had a nearly 60% increased risk of breast cancer among those who had ever used hormonal birth control, while never users had a significantly reduced risk (Pinteraction=0.01). Among postmenopausal women, those with genotypes lacking a (CA)19 repeat allele had significantly increased breast cancer risk among subjects with a lower than median body mass index (BMI) (OR=1.77 95% CI=1.09, 2.87), while no association for IGF1 genotype was seen among women with a higher than median BMI (Pinteraction=0.04). Our results demonstrate a role for alleles with fewer than (CA)19 repeats as a risk factor for breast cancer and also suggest that several traditional breast cancer risk factors modify the association of the IGF1 (CA)19 repeat genotype.

Gender and age in the biochemical assessment of cure of acromegaly

The principal biochemical criteria for cure in acromegaly are normalization of both glucose-suppressed GH levels and IGF-I levels. As we have reported previously, measurement of GH by highly sensitive assay in conjunction with IGF-I levels has led to a re-appraisal of "normal" GH suppression criteria during an OGTT in subjects with acromegaly. In some patients with active acromegaly, glucose-suppressed GH levels as measured by highly sensitive assay are much lower than could previously be appreciated with less sensitive GH assays and some other patients in apparent remission have subtle abnormalities of GH suppression. A question to arise is whether gender differences in glucose-suppressed GH levels as found by others in young healthy subjects should be considered in our interpretation of OGTT criteria for cure in acromegaly. Therefore, we have evaluated parameters of GH secretion in a larger number of subjects from our cohort of postoperative patients with acromegaly and in healthy subjects in order to determine if gender or age associated differences in these parameters exist. Ninety-two subjects with acromegaly (49 men, 43 women) and 46 age-matched healthy subjects (26 men, 20 women) were evaluated with baseline GH and IGF-I levels and nadir GH levels after a 100 g. OGTT. GH was assayed by highly sensitive IRMA (DSL). Basal GH levels were higher in female than in male healthy subjects, but the fall in GH from baseline (% suppression) was also greater in females resulting in no significant difference in mean nadir GH levels in female vs. male healthy subjects (0.09 vs. 0.08 microg/L). In the subjects with acromegaly, there were no significant gender differences in basal, %GH suppression or nadir GH levels. Basal and nadir GH levels correlated significantly only in subjects with active disease (r=0.84, p<.0001). Similarly, IGF-I levels correlated significantly with basal (r=0.573, p=.0012), and nadir (r=.702, p<.0001) GH levels only in subjects with active disease. Gender differences in IGF-I levels were not apparent in any group of subjects. As expected, IGF-I levels declined with age in those groups of subjects with normal IGF-I levels. Nadir GH levels did not vary with age. In conclusion, we have not found significant gender or age-related differences in nadir GH levels and thus our data does not support separate OGTT criteria for cure in men and women with acromegaly.

Insulin-Like growth factor I: implications in aging

According to the somatomedin model, growth hormone (GH)-dependent hepatic synthesis is responsible for maintaining circulating insulin-like growth factor (IGF)-I levels. On the other hand, the local autocrine/paracrine IGF-I expression in peripheral tissue is generally GH-independent and reflects the effects of various and tissue-specific trophic hormones. Circulating IGF-I levels undergo important age-related variations increasing at puberty and decreasing, thereafter, to low levels in the elderly. Low IGF-I levels in the elderly mainly reflect impaired somatotroph secretion but the decline in gonadal sex steroid levels, some protein and micronutrients malnutrition as well as age-dependent variations in IGF-binding proteins may also play a role in the age-related decrease in IGF-I activity. This, in turn, partially accounts for age-related changes in bones, muscles, cardiovascular system, central nervous system and the immune system. However, it is currently unclear whether treatment with exogenous IGF-I can retard or reverse age-related changes in body structure and function.