Effect of estrogen status on bone regulating hormones

Effect of surgical and natural menopause on proximal femur morphometry in obese women

The purpose of this study is to determine whether there are differences in proximal femur parameters of women subjected to menopause surgically or naturally. In this study, 10 parameters belonging to proximal femur of a total of 60 women cases of whom 30 had a mean age of 55.53 ± 4.57 years; body mass index, 33.06 ± 4.21 kg/m²; menopause age, 48.10 ± 5.92; and menopause years, 7.50 ± 4.58; and who were subjected to natural menopause; and 30 women whose mean age was 56.10 ± 6.87 years; body mass index, 33.33 ± 3.76 kg/m²; menopause age, 48.00 ± 4.64 years and menopause year, 8.10 ± 7.29; who were subjected to surgical menopause, and who did not use hormone replacement, were examined by radiography. Their anthropometric measurements, body compositions, blood hormone analyses (FSH, LH, estradiol, progesterone) and bone mineral densities (femur neck, femur total, lumbar t-score) were evaluated. It was found that there was no difference between surgical and natural menopause with respect to proximal femur parameters (p > 0.05). It was also found that FSH levels were high in the surgical menopause group and there were significant differences between the groups (p < 0.040). No significant difference was found even though bone mineral density t-score tests were lower in the surgical menopause group (p > 0.05). It was found that the difference in low bone mineral density level and high FSH values in the surgical menopause group do not have a relationship with proximal femur morphometry. It was determined that even though the women did not have ovaries, there was no difference between surgical menopause women and natural menopause women with respect to proximal femur morphometry.

Body composition, visceral fat distribution and fat oxidation in postmenopausal women using oral or transdermal oestrogen

OBJECTIVES

The aim of this study was to observe hysterectomized postmenopausal women (without progestogen, which could interfere in the results), using oral-conjugated oestrogen 0.625 mg daily (n=13) or 17beta-estradiol transdermal patches delivering 50 microg daily (n=10) during 12 months, and to evaluate the treatment effects on body composition, visceral fat distribution, energy expenditure and substrate oxidation.

METHODS

We studied 23 postmenopausal women using oral-conjugated oestrogen (Premarin) 0.625 mg daily (n=13) or transdermal oestrogen patches (Systen TTS) 50 microg daily (n=10). Body composition was measured by DEXA, visceral adipose tissue areas were measured by abdominal computed tomography, and energy expenditure, fat oxidation and carbohydrate oxidation were measured by indirect calorimetry (Deltatrac Metabolic Monitor).

RESULTS

There were: (1) a decrease in IGF-I and an increase in GH levels in the oral group and no change in the transdermal group; (2) a increase in lean body mass in the transdermal group and a decrease in the oral group; (3) a increase in total body fat mass in the oral group and no change in the transdermal group; (4) an increases in total bone mass and in total bone mineral density in the transdermal group and no change in the oral group; (5) an increase in lipid oxidation in the transdermal group and a decrease in the oral group, and (6) no significantly change about weight, visceral adipose tissue areas and energy expenditure in both groups.

CONCLUSIONS

The administration route of oestrogen replacement therapy in postmenopausal women confers distinct and divergent effects on body composition and substrate oxidation during 12-months treatment.

The impact of subcutaneous oestradiol implants on biochemical markers of bone turnover and bone mineral density in postmenopausal women

OBJECTIVE

To evaluate the anabolic effect of oestrogen on bone by comparing the response of markers of bone formation (and resorption) and bone mineral density (BMD) to subcutaneous oestradiol implants.

DESIGN

One year double-blind placebo controlled randomised study.

SETTING

Clinical research unit within a teaching hospital.

POPULATION

Twenty-one hysterectomised postmenopausal women were randomised to 25 mg oestradiol implants at baseline and at six months or to have a sham procedure at baseline and six months.

METHODS

BMD and quantitative ultrasound (QUS) were assessed at baseline and one year. Bone alkaline phosphatase (bone ALP), procollagen type I N-terminal propeptide (PINP), osteocalcin (OC), free deoxypyridinoline (iFDPD), N-telopeptide of type I collagen (NTX), serum oestradiol and intact parathyroid hormone (PTH) were measured at baseline, 4, 8, 12 and 24 weeks.

MAIN OUTCOME MEASURES

Percentage change markers of bone turnover and PTH and change in oestradiol levels over first six months and percentage of changes in DXA and QUS over one year.

RESULTS

PINP, bone ALP and OC increased by 28%, 7% and 9%, respectively (P < 0.01) during the first four weeks of treatment and then decreased significantly. Lumbar spine (LS) and total hip (TH) BMD increased by 5.4% and 6.0% (P < 0.001), respectively, and femoral neck (FN) BMD by 3.7% (P < 0.05) during the first year of treatment compared with control subjects. The peak serum oestradiol level was achieved four weeks after implant insertion. Mean PTH levels increased significantly in subjects receiving subcutaneous oestradiol.

CONCLUSION

Subcutaneous oestrogen exerted an apparent anabolic effect on bone, which was initially reflected by an increase in bone formation markers and later by a large increase in BMD.

Effects of the selective oestrogen receptor modulator-raloxifene-on calcium and PTH secretory dynamics in women with osteoporosis

OBJECTIVES

A possible mechanism for the maintenance of bone mass by oestrogens and the selective oestrogen receptor modulator (SERM)-raloxifene-is an interaction with calciotropic hormones. We studied the effects of raloxifene on calcium-PTH homeostasis.

PATIENTS AND MEASUREMENTS

Calcium and EDTA infusions were performed in 32 post-menopausal women with osteoporosis (BMD T score < - 2.5). This cross-sectional study was performed in the third year of the MORE (Multiple Outcomes of Raloxifene Evaluation) trial, a double-blind, placebo-controlled study. After an overnight fast, calcium glubionate (5 mg/kg BW*h), and after 2.5 h of test-free interval, Na3EDTA (40 mg/kg BW*h) were given intravenously. The duration of infusions was based on individual plasma total calcium before the calcium infusion (t = 0), the target calcium (2.60 and 1.95 mmol/l, respectively), and desired mean calcium change (0.010 mmol/L*min). Blood samples were taken at 0 and every 5 minutes of both infusions. Plasma PTH levels were fitted into an inversed sigmoidal relation with plasma calcium. The effect of raloxifene on calcium-PTH homeostasis was tested in linear regression models adjusted for age and BMI. Nine patients used placebo, 13 raloxifene 60 mg/day and 10 raloxifene 120 mg/day.

RESULTS

Raloxifene use was associated with lower plasma albumin (40.7 +/- 1.8 vs. 38.0 +/- 2.0 and 38.5 +/- 2.3 g/l, for placebo, raloxifene 60 mg/day and raloxifene 120 mg/day, respectively, P = 0.01), lower plasma total calcium at t = 0 (2.28 vs. 2.24 and 2.21; +/- 0.07 mmol/L; P = 0.03), lower plasma total calcium at 50% of maximal PTH secretion (PTH set-point: 2.23 +/- 0.06 vs. 2.18 +/- 0.07 and 2.16 +/- 0.08 mmol/l, P = 0.06), and lower plasma non-suppressible PTH (0.84 +/- 0.19 vs. 0.75 +/- 0.10 and 0.73 +/- 0.05 pmol/l, P = 0.02). After correction for plasma albumin, the differences for plasma calcium at t = 0 and at PTH set-point were no longer significant. In contrast, the difference in PTH suppression during calcium load was not explained either by differences in plasma albumin or calcium.

CONCLUSION

Raloxifene did not have any detectable effect on the PTH set-point. An effect on non-suppressible PTH secretion cannot be excluded.

Relative contributions of testosterone and estrogen in regulating bone resorption and formation in normal elderly men

Young adult males who cannot produce or respond to estrogen (E) are osteopenic, suggesting that E may regulate bone turnover in men, as well as in women. Both bioavailable E and testosterone (T) decrease substantially in aging men, but it is unclear which deficiency is the more important factor contributing to the increased bone resorption and impaired bone formation that leads to their bone loss. Thus, we addressed this issue directly by eliminating endogenous T and E production in 59 elderly men (mean age 68 years), studying them first under conditions of physiologic T and E replacement and then assessing the impact on bone turnover of withdrawing both T and E, withdrawing only T, or only E, or continuing both. Bone resorption markers increased significantly in the absence of both hormones and were unchanged in men receiving both hormones. By two-factor ANOVA, E played the major role in preventing the increase in the bone resorption markers, whereas T had no significant effect. By contrast, serum osteocalcin, a bone formation marker, decreased in the absence of both hormones, and both E and T maintained osteocalcin levels. We conclude that in aging men, E is the dominant sex steroid regulating bone resorption, whereas both E and T are important in maintaining bone formation.

Parathyroid hormone regulates transforming growth factor beta1 and beta2 synthesis in osteoblasts via divergent signaling pathways

Parathyroid hormone 1-34 [PTH(1-34)] was shown to increase transforming growth factor beta1 (TGF-beta1) and TGF-beta2 concentrations in supernatants of cultured human osteoblasts and to increase TGF-beta1 and TGF-beta2 messenger RNA (mRNA) concentrations and gene transcription in these cells. Because PTH(1-34) activates both protein kinase C (PKC) and protein kinase A (PKA) pathways in osteoblasts, we investigated the role of each kinase pathway in activation of TGF-beta isoforms. PTH(29-32), which activates the PKC pathway in rat osteoblasts, increased TGF-beta1 but not TGF-beta2 concentrations in supernatants of osteoblasts. Phorbol myristate acetate (PMA), a PKC agonist, increased TGF-beta1 but not TGF-beta2 concentrations. Specific PKC antagonists safingol and Gö6976 attenuated PTH(1-34)-mediated increases in TGF-beta1 but not TGF-beta2 synthesis. PTH(1-31), which increases PKA activity in several cell culture systems, increased TGF-beta2 but not TGF-beta1 concentrations in human osteoblast supernatants. Forskolin, a PKA agonist, increased TGF-beta2 but not TGF-beta1 concentrations in supernatants of human osteoblasts. The PKA antagonist H-89 blunted PTH(1-34)-mediated increases in TGF-beta2 but not TGF-beta1 synthesis. Our results are consistent with the concept that PTH increases TGF-beta1 expression and secretion by pathways that involve the PKC pathway, whereas it increases TGF-beta2 expression and secretion via the PKA pathway.

Composição corpórea, distribuição de gordura e metabolismo de repouso em mulheres histerectomizadas no climatério: há diferenças de acordo com a forma da administração do estrogênio?

As mulheres no climatério sofrem inúmeras alterações metabólicas, cardiovasculares e de composição corporal. A terapêutica de reposição hormonal (TRH) vem alcançando importância na atualidade, tornando-se quase um consenso que a mulher após a menopausa deve receber hormônios, pelos benefícios que trazem para a saúde, tais como prevenção de doenças coronarianas e osteoporose. A forma de administração de estrogênios influi em uma série de parâmetros metabólicos; é sabido, por exemplo, que a administração oral provoca uma elevação no hormônio de crescimento (GH) e uma diminuição do IGFI: quanto à forma (transdérmica), os estudos ainda não são conclusivos quanto aos níveis do GH e IGFI. Por outro lado, o GH e o IGFI podem agir de maneiras diferentes no metabolismo lipídico, ósseo e na distribuição de gordura corpórea. O objetivo deste trabalho foi estudar as variações da distribuição visceral de gordura nas diferentes formas de administração estrogênica e, particularmente, verificar se a forma de administração do hormônio altera a quantidade de gordura visceral. Foram estudadas 33 mulheres no climatério, histerectomizadas, divididas em 3 grupos: 1) 13 pacientes recebendo estrogênio eqüino conjugado 0,625mg via oral diariamente; 2) 10 pacientes recebendo 17b estradiol TTS 50 2x/semana via transdérmica e; 3) 10 pacientes recebendo placebo. Estas pacientes foram submetidas: a) análise da composição corporal pelos métodos de bioimpedância (RJL 101-A) e densitometria óssea e corpórea (DEXA); b) análise da distribuição de gordura, particularmente de adiposidade visceral, pela tomografia computadorizada abdominal e; c) medida do metabolismo de repouso pelo calorímetro DELTA-TRAC. Foram ainda feitas dosagens laboratoriais de colesterol total e frações, triglicérides e glicemia aos 0,6 e 12 meses. Não observamos diferenças estatística significativas nos parâmetros estudados em nenhum dos 3 grupos (placebo, estrógeno oral e estrogênio transdérmico), embora notamos tendência a maior ganho de peso nos grupos com estrógenos e tendência a maior ganho de massa magra no grupo com estrogênio transdérmico.

Calcitonin reserve in different stages of atrophic autoimmune thyroiditis

The objective of this study was to determine the calcitonin (CT) hormone reserve in different severity of atrophic autoimmune thyroiditis (AAT). Forty-eight female patients with AAT were divided into four groups based on basal and peak thyrotropin (TSH) values (after oral thyrotropin-releasing hormone [TRH], free triiodothyronine (FT3) and free thyroxine (FT4) ranging from normal in group 1 to overt hypothyroidism in group 4. All had thyroid antibodies. The control group comprised euthyroid females of comparable age, without thyroid antibodies. Basal CT and CT response to calcium infusion (area under the curve) were investigated as parameters of CT reserve. Basal CT was lower in groups 2 to 4 of patients with AAT (compared to controls), but the difference was not significant. Stimulated CT levels were lower (p < 0.05) in all groups of patients compared to controls, with markedly reduced CT-secretory reserve in group 4. Thyroid antibody concentrations and, basal and postinfusion calcium levels were not significantly different among the various groups. In conclusion CT deficiency (especially stimulated values) occurs in AAT and is more severe in hypothyroid patients than in earlier stages of AAT.

Effect of short-term medroxyprogesterone acetate on left ventricular mass: role of insulin-like growth factor-1

Previous studies using 17beta-estradiol and medroxyprogesterone acetate (MPA) have shown that hormone replacement therapy (HRT) increases left ventricular mass (LVM). To determine if insulin-like growth factor-1 (IGF-1) is associated with the increase in LVM, we measured IGF-1 and IGF-binding protein-3 (IGFBP-3) levels in 19 postmenopausal women before and after 8 weeks of oral treatment with MPA 5 mg/d. LVM was measured by two-dimensional echocardiography. Changes in IGF-1, IGFBP-3, and LVM from baseline were analyzed by paired ttest. Regression analysis was used to determine if changes in the IGF-1 axis with MPA treatment affect the increase in LVM. LVM increased 4.4% during the study (P = .006 vbaseline). IGF-1 increased 17% with MPA (P = .008), whereas IGFBP-3 did not change. The IGF-1/IGFBP-3 ratio increased 16.8% (P = .0003). Regression analysis of LVM with IGF-1, IGFBP-3, and the IGF-1/IGFBP-3 ratio suggested that IGF-1 during MPA therapy explains 2.4% and the IGF-1/IGFBP-3 ratio explains 3.2% of the variation in LVM. There was no effect of IGFBP-3 on LVM. Most of the variation in LVM with MPA (90.5%) was explained by baseline LVM. The IGF-1/IGFBP-3 ratio on MPA treatment was inversely related to the change in LVM: women with a lower LVM at baseline had the greatest increase in LVM with MPA. These findings suggest that MPA increases IGF-1 and LVM. Because the increase in IGF-1 with MPA treatment explains a fraction of the increase in LVM, other mechanisms must also be operative.

Gender differences in insulin-like growth factor and bone mineral density association in old age: the Rancho Bernardo Study

Insulin-like growth factor-I (IGF-I) clearly plays a role in bone metabolism and maintenance, as evidenced by in vitro and animal studies. In clinical studies, the age-related decrease in IGF-I parallels the age-related decrease in bone mineral density (BMD), but several age-adjusted cross-sectional studies show no consistent association of IGF-I and BMD. We report here a cross-sectional study of serum IGF-I and BMD levels in 483 men and 455 postmenopausal women not using estrogen; subjects were 55 years of age and older, community-dwelling, ambulatory, and unselected for bone density. IGF-I was measured by a highly specific radioimmunoassay. BMD was measured at the lumbar spine and hip using dual-energy X-ray absorptiometry. Men had higher IGF-I and BMD levels than women. In age-adjusted and age-stratified models, IGF-I was associated with BMD only in women (test for interaction, p < 0.0001). Gender differences persisted in gender-specific multiple regression analyses adjusted for age, body mass index, thiazide diuretic use, current smoking, alcohol intake, physical activity, and weight change; IGF-I was significantly associated with BMD at the spine (p = 0.0001) and hip (p = 0.02) in women, but not in men (p's > 0.6). Circulating estradiol levels were not associated with IGF-I levels in either gender, testosterone was inversely associated with IGF-I and only in men. This striking gender difference has not been described previously. Its etiology is unknown. The answer could lead to improved understanding of gender differences in osteoporosis and in response to treatment with IGF-I or growth hormone.

17beta-estradiol potently suppresses cAMP-induced insulin-like growth factor-I gene activation in primary rat osteoblast cultures

Insulin-like growth factor-I (IGF-I) is a key factor in bone remodeling. In osteoblasts, IGF-I synthesis is enhanced by parathyroid hormone and prostaglandin E2 (PGE2) through cAMP-activated protein kinase. In rats, estrogen loss after ovariectomy leads to a rise in serum IGF-I and an increase in bone remodeling, both of which are reversed by estrogen treatment. To examine estrogen-dependent regulation of IGF-I expression at the molecular level, primary fetal rat osteoblasts were co-transfected with the estrogen receptor (hER, to ensure active ER expression), and luciferase reporter plasmids controlled by promoter 1 of the rat IGF-I gene (IGF-I P1), used exclusively in these cells. As reported, 1 microM PGE2 increased IGF-I P1 activity by 5-fold. 17beta-Estradiol alone had no effect, but dose-dependently suppressed the stimulatory effect of PGE2 by up to 90% (ED50 approximately 0.1 nM). This occurred within 3 h, persisted for at least 16 h, required ER, and appeared specific, since 17alpha-estradiol was 100-300-fold less effective. By contrast, 17beta-estradiol stimulated estrogen response element (ERE)-dependent reporter expression by up to 10-fold. 17beta-Estradiol also suppressed an IGF-I P1 construct retaining only minimal promoter sequence required for cAMP-dependent gene activation, but did not affect the 60-fold increase in cAMP induced by PGE2. There is no consensus ERE in rat IGF-I P1, suggesting novel downstream interactions in the cAMP pathway that normally enhances IGF-I expression in skeletal cells. To explore this, nuclear extract from osteoblasts expressing hER were examined by electrophoretic mobility shift assay using the atypical cAMP response element in IGF-I P1. Estrogen alone did not cause DNA-protein binding, while PGE2 induced a characteristic gel shift complex. Co-treatment with both hormones caused a gel shift greatly diminished in intensity, consistent with their combined effects on IGF-I promoter activity. Nonetheless, hER did not bind IGF-I cAMP response element or any adjacent sequences. These results provide new molecular evidence that estrogen may temper the biological effects of hormones acting through cAMP to regulate skeletal IGF-I expression and activity.