Insulin-Like Growth Factor I Levels in Healthy Adults

Cardiometabolic Changes in Response to a Calorie-Restricted DASH Diet in Obese Older Adults

Objective: To examine the response of a calorie-restricted Dietary Approaches to Stop Hypertension diet on indicators of cardiometabolic health in a cohort of sedentary obese older adults. Design: This was a controlled-feeding trial with a parallel design. Each participant consumed either 3 oz (85 g; n = 15) or 6 oz (170.1 g; n = 13) of lean fresh beef within a standardized calorie-restricted DASH-like diet for 12-weeks. Fasted blood samples were collected and used to measure conventional biomarkers of cardiovascular, metabolic and inflammatory health. Participants: Caucasian older (70.8 years), obese (BMI: 32 ± 6.9 kg/m²; WC: 101 ± 16.4 cm) females (n = 17) and males (n = 11) from the rural community of Brookings, South Dakota. Results: 28 participants completed the 12-week feeding trial, with no differences (p > 0.05) among the biomarkers of cardiometabolic health between the 3 and 6 oz beef intake groups. However, when the beef intake groups were combined, all biomarkers changed concentration in response to the intervention diet. Total cholesterol (p < 0.001), LDL-C (p = 0.004), HDL-C (p < 0.0001), insulin (p = 0.014), glucose (p = 0.008), HOMA-IR (p < 0.05), IL-12 (p < 0.001), and CRP (p = 0.006) all decreased in response to the study diet. IGF-1 (p < 0.001) and IL-8 (p = 0.005) increased in response to the intervention. Correlations among cardiometabolic biomarkers and body composition measures were observed. By study end, the decrease in insulin (R ² = 0.22; P = 0.012) and HOMA-IR (R ² = 0.22; P = 0.01) was positively correlated with the decrease in waist circumference. The increase in IGF-1 was significantly correlated with the decrease in waist circumference (R ² = 0.21; p = 0.014). The increase in IGF-1 was significantly correlated with the increase in sit-to-stand (R ² = 0.21; p = 0.016). The increase in IL-8 was significantly correlated with decreases in total cholesterol (R ² = 0.24; P = 0.008), LDL-C (R ² = 0.17; P = 0.031) and glucose (R ² = 0.44; P = 0.0001). Conclusions: These findings suggest that a DASH-like diet with restricted calories may potentially improve biomarkers of cardiometabolic health in sedentary obese older adults. These results also point to interrelationships between body composition changes and changes in cardiometabolic biomarkers. Lastly, regardless of meat intake amount, positive impacts on cardiometabolic biomarkers were observed in this cohort of older adults with an obese phenotype.

Biomarkers of Insulin and the Insulin-Like Growth Factor Axis in Relation to Breast Cancer Risk in Chinese Women

BACKGROUND

The interplay between biomarkers of insulin and the insulin-like growth factor (IGF) axis in the context of breast cancer risk is unclear.

METHODS

We measured the concentrations of insulin, C-peptide, IGF1, and IGF binding protein 3 (IGFBP3) and calculated the homeostasis model assessment of insulin resistance (HOMA-IR) index and the IGF1/IGFBP3 ratio among 2536 patients with breast cancer and 2528 patients with benign breast disease recruited from Ruijin Hospital, Shanghai, China, between 2012 and 2017.

RESULTS

Multivariable-adjusted odds ratios (ORs) for breast cancer associated with the highest quartiles versus the lowest quartiles of insulin and IGF factors were 1.45 (95% CI, 1.20-1.75) for insulin, 1.32 (1.08-1.60) for C-peptide, 1.53 (1.26-1.85) for HOMA-IR, and 1.27 (1.05-1.53) for IGF1; these associations did not differ substantially across stratifications of age, body mass index, age at menarche, or menopausal status (all P for interaction >0.05). In the joint analysis, the highest quartile of IGF1 was associated with the greatest risk of breast cancer in the highest quartiles of insulin (OR, 1.77; 95% CI, 1.29-2.44), C-peptide (1.60; 1.17-2.20), and HOMA-IR (1.90; 1.38-2.62), compared with the risks associated with the combination of the lowest quartiles of IGF1 and each insulin factor. In stratification analysis, the positive association between IGF1 and breast cancer was stronger in the highest quartiles of insulin (P[interaction] = 0.29), C-peptide (P[interaction] = 0.020), and HOMA-IR (P[interaction] = 0.075).

CONCLUSION

Our findings indicate effect modifications of insulin, C-peptide, and insulin resistance on the relationship between IGF1 and breast cancer risk in Chinese women.

The effect of soy intervention on insulin-like growth factor 1 levels: A meta-analysis of clinical trials

A low insulin-like growth factor 1 (IGF-1) level is known to be associated with many disorders. Several studies have shown that soy consumption may influence IGF-1, but the findings remain inconclusive. In this work, we conducted a systematic review and meta-analysis to provide a more accurate estimation of the effect of soy consumption on plasma IGF-1. A comprehensive systematic search was performed in Scopus, Embase, Web of Science, and PubMed/MEDLINE databases from inception until October 2019. Eight studies fulfilled the eligibility criteria. The pooled weighted mean difference (WMD) of the eligible studies was calculated with random-effects approach. Overall, a significant increment in plasma IGF-1 was observed following soy intervention (WMD: 13.5 ng/ml, 95% CI: 5.2, 21.8, I2 = 97%). Subgroup analyses demonstrated a significantly greater increase in IGF-1, when soy was administered at a dosage of ≤40 g/day (WMD: 11.7 ng/ml, 95% CI: 10.9 to 12.6, I2 = 98%), and when the intervention duration was <12 weeks (WMD: 26.6 ng/ml, 95% CI: 9.1 to 44.1, I2 = 0.0%). In addition, soy intervention resulted in a greater increase in IGF-1 among non-healthy subjects (WMD: 36 ng/ml, 95% CI: 32.7 to 39.4, I2 = 84%) than healthy subjects (WMD: 9.8 ng/ml, 95% CI: 8.9 to 10.7, I2 = 90%). In conclusion, this study provided the first meta-analytical evidence that soy intake may increase IGF-1 levels, but the magnitude of the increase is dependent on the intervention dosage, duration, and health status of the participants.

Relationship of circulating insulin-like growth factor-I and binding proteins 1-7 with mammographic density among women undergoing image-guided diagnostic breast biopsy

Background

Mammographic density (MD) is a strong breast cancer risk factor that reflects fibroglandular and adipose tissue composition, but its biologic underpinnings are poorly understood. Insulin-like growth factor binding proteins (IGFBPs) are markers that may be associated with MD given their hypothesized role in breast carcinogenesis. IGFBPs sequester IGF-I, limiting its bioavailability. Prior studies have found positive associations between circulating IGF-I and the IGF-I:IGFBP-3 ratio and breast cancer risk. We evaluated the associations of IGF-I, IGFBP-3, and six other IGFBPs with MD.

Methods

Serum IGF measures were quantified in 296 women, ages 40–65, undergoing diagnostic image-guided breast biopsy. Volumetric density measures (MD-V) were assessed in pre-biopsy digital mammograms using single X-ray absorptiometry. Area density measures (MD-A) were estimated by computer-assisted thresholding software. Age, body mass index (BMI), and BMI²-adjusted linear regression models were used to examine associations of serum IGF measures with MD. Effect modification by BMI was also assessed.

Results

IGF-I and IGFBP-3 were not strongly associated with MD after BMI adjustment. In multivariable analyses among premenopausal women, IGFBP-2 was positively associated with both percent MD-V (β = 1.49, p value = 0.02) and MD-A (β = 1.55, p value = 0.05). Among postmenopausal women, positive relationships between IGFBP-2 and percent MD-V (β = 2.04, p = 0.003) were observed; the positive associations between IGFBP-2 and percent MD-V were stronger among lean women (BMI < 25 kg/m²) (β = 5.32, p = 0.0002; p interaction = 0.0003).

Conclusions

In this comprehensive study of IGFBPs and MD, we observed a novel positive association between IGFBP-2 and MD, particularly among women with lower BMI. In concert with in vitro studies suggesting a dual role of IGFBP-2 on breast tissue, promoting cell proliferation as well as inhibiting tumorigenesis, our findings suggest that further studies assessing the role of IGFBP-2 in breast tissue composition, in addition to IGF-1 and IGFBP-3, are warranted.

Electronic supplementary material

The online version of this article (10.1186/s13058-019-1162-8) contains supplementary material, which is available to authorized users.

Effects of IGF-1 isoforms on muscle growth and sarcopenia

The decline in skeletal muscle mass and strength occurring in aging, referred as sarcopenia, is the result of many factors including an imbalance between protein synthesis and degradation, changes in metabolic/hormonal status, and in circulating levels of inflammatory mediators. Thus, factors that increase muscle mass and promote anabolic pathways might be of therapeutic benefit to counteract sarcopenia. Among these, the insulin‐like growth factor‐1 (IGF‐1) has been implicated in many anabolic pathways in skeletal muscle. IGF‐1 exists in different isoforms that might exert different role in skeletal muscle. Here we study the effects of two full propeptides IGF‐1Ea and IGF‐1Eb in skeletal muscle, with the aim to define whether and through which mechanisms their overexpression impacts muscle aging. We report that only IGF‐1Ea expression promotes a pronounced hypertrophic phenotype in young mice, which is maintained in aged mice. Nevertheless, examination of aged transgenic mice revealed that the local expression of either IGF‐1Ea or IGF‐1Eb transgenes was protective against age‐related loss of muscle mass and force. At molecular level, both isoforms activate the autophagy/lysosome system, normally altered during aging, and increase PGC1‐α expression, modulating mitochondrial function, ROS detoxification, and the basal inflammatory state occurring at old age. Moreover, morphological integrity of neuromuscular junctions was maintained and preserved in both MLC/IGF‐1Ea and MLC/IGF‐1Eb mice during aging. These data suggest that IGF‐1 is a promising therapeutic agent in staving off advancing muscle weakness.

Serum insulin-like growth factor (IGF)-I and IGF binding protein-3 in relation to terminal duct lobular unit involution of the normal breast in Caucasian and African American women: The Susan G. Komen Tissue Bank

Lesser degrees of terminal duct lobular unit (TDLU) involution, as reflected by higher numbers of TDLUs and acini/TDLU, are associated with elevated breast cancer risk. In rodent models, the insulin-like growth factor (IGF) system regulates involution of the mammary gland. We examined associations of circulating IGF measures with TDLU involution in normal breast tissues among women without precancerous lesions. Among 715 Caucasian and 283 African American (AA) women who donated normal breast tissue samples to the Komen Tissue Bank between 2009 and 2012 (75% premenopausal), serum concentrations of IGF-I and binding protein (IGFBP)-3 were quantified using enzyme-linked immunosorbent assay. Hematoxilyn and eosin-stained tissue sections were assessed for numbers of TDLUs ("TDLU count"). Zero-inflated Poisson regression models with a robust variance estimator were used to estimate relative risks (RRs) for association of IGF measures (tertiles) with TDLU count by race and menopausal status, adjusting for potential confounders. AA (vs. Caucasian) women had higher age-adjusted mean levels of serum IGF-I (137 vs. 131 ng/mL, p = 0.07) and lower levels of IGFBP-3 (4165 vs. 4684 ng/mL, p < 0.0001). Postmenopausal IGFBP-3 was inversely associated with TDLU count among AA (RR_T3vs.T1  = 0.49, 95% CI = 0.28-0.84, p-trend = 0.04) and Caucasian (RR_T3vs.T1 =0.64, 95% CI = 0.42-0.98, p-trend = 0.04) women. In premenopausal women, higher IGF-I:IGFBP-3 ratios were associated with higher TDLU count in Caucasian (RR_T3vs.T1 =1.33, 95% CI = 1.02-1.75, p-trend = 0.04), but not in AA (RR_T3vs.T1 =0.65, 95% CI = 0.42-1.00, p-trend = 0.05), women. Our data suggest a role of the IGF system, particularly IGFBP-3, in TDLU involution of the normal breast, a breast cancer risk factor, among Caucasian and AA women.

The relationship between serum IGF-1, handgrip strength, physical performance and falls in elderly men and women

OBJECTIVE

Human aging is accompanied by a decrease in growth hormone secretion and serum insulin-like growth factor (IGF)-1 levels. Also, loss of muscle mass and strength and impairment of physical performance, ending in a state of frailty, are seen in elderly. We aimed to investigate whether handgrip strength, physical performance and recurrent falls are related to serum IGF-1 levels in community-dwelling elderly.

DESIGN

Observational cohort study (cross-sectional and prospective).

METHODS

We studied the association between IGF-1 and handgrip strength, physical performance and falls in participants of the Longitudinal Aging Study Amsterdam. A total of 1292 participants were included (633 men, 659 women). Serum IGF-1 levels were divided into quartiles (IGF-1-Q1 to IGF-1-Q4). Data on falls were collected prospectively for a period of 3 years. All analyses were stratified for age and physical activity and adjusted for relevant confounders.

RESULTS

Men with a low physical activity score in IGF-1-Q1 and IGF-1-Q2 of the younger age group had a lower handgrip strength compared to IGF-1-Q4. In younger more active males in IGF-1-Q2 physical performance was worse. Recurrent fallers were less prevalent in older, low active males with low IGF-1 levels. In females, recurrent fallers were more prevalent in older, more active females in IGF-1-Q2. IGF-1 quartile may predict changes in handgrip strength and physical performance in men and women.

CONCLUSIONS

Our results indicate that lower IGF-1 levels are associated with lower handgrip strength and worse physical performance, but less recurrent fallers especially in men. Associations were often more robust in IGF-1-Q2. Future studies on this topic are desirable.

Reference ranges for serum insulin-like growth factor I (IGF-I) in healthy Chinese adults

Purpose

To determine serum insulin-like growth factor 1 (IGF-I) levels in healthy Chinese adults, establish reference ranges for serum IGF-I levels and observe the effects of age, sex, body mass index (BMI) and geographical region on serum IGF-I levels.

Methods

In total, 2791 healthy adults (1339 males and 1452 females) from the north (Beijing) and south (Guizhou Province) of China were recruited following a questionnaire survey, physical examination and laboratory examination. Both sexes were divided into 13 groups according to age (18, 19, 20–24, 25–29, 30–34, 35–39, 40–44, 45–49, 50–54, 55–59, 60–64, 65–69 and ≥70 years). The serum IGF-I levels were measured by performing a chemiluminescent assay (Immulite 2000®), and the LMS (Lambda-Mu-Sigma) method was applied to construct smooth centile curves of age-specific IGF-I levels.

Results

Serum IGF-I levels in the adults gradually decreased with increasing age from 18 to 70 years in both the male and female participants. Although the decrease in the level of IGF-1 was more pronounced in females than in males, no significant difference was observed between the sexes, except in the 60- to 64-year-old age group (P = 0.0329). The multiple linear regression model showed that there was an inverse relationship between the serum IGF-I level and BMI (P<0.001), and the serum IGF-I level in the Guizhou population was higher than that in the Beijing population (P<0.05).

Conclusion

The normal reference ranges for age- and sex-specific serum IGF-I levels were established for the first time in a large sample of Chinese adults. The serum IGF-I levels were significantly influenced by age, BMI and geographical region.

Acute effects of physical exercise on the serum insulin-like growth factor system in women with fibromyalgia

BACKGROUND

Increased Serum insulin-like growth factor-1 (S-IGF-1) has been noted after physical activity in healthy subjects, while the acute release of S-IGF-1 in relation to exercise has not previously been studied in women with fibromyalgia (FM). S-IGF-1 and its binding protein (S-IGFBP-3) are mediated by growth hormone and have anabolic effects on the skeletal muscle. Aim of the study was to investigate acute release of IGF-1 after aerobic exercise in women with FM.

METHODS

The acute effect of physical exercise on S-IGF-1 and S-IGFBP-3 were studied in 22 women with FM and in 27 healthy controls during moderate and high-intensity cycling (i.e. ratings 12-13 and 15-17, on Borg's perceived exertion scale (RPE), respectively). Self-reported pain and fatigue were recorded. Differences within and between the two groups were analyzed.

RESULTS

After 15 min of bicycling, S-IGF-1 and S-IGFBP-3 increased both within the group with FM and in the healthy controls (p < 0.01). The increases in S-IGF-1 did not significantly differ between the women with FM and the healthy control group (mean increase 11 ± 10 vs. 11 ± 15 ng/ml and 13 ± 10 vs. 19 ± 22 ng/ml) when bicycling at moderate or high intensity, respectively. Self-reported pain and fatigue during exercise, irrespective of intensity, were higher in women with FM compared with healthy controls (p < 0.001).

CONCLUSIONS

Fifteen minutes bicycling at moderate intensity was sufficient to acutely mobilise S-IGF-1 in women with FM similarly to healthy controls in spite of higher score of fatigue and pain in women with FM. Hence, patients with FM were able to activate their skeletal muscle metabolism during a short, moderate bout of exercise and were not resistant to training effects. The result is important for encouraging clinical rehabilitation of patients with FM who commonly exercise at a moderate, rather than at a high-intensity level.

TRIAL REGISTRATION

ClinicalTrials.govNCT01592916 , May 4, 2012.

Analysis of multipotent mesenchymal stromal cells used for acute graft-versus-host disease prophylaxis

BACKGROUND

Multipotent mesenchymal stromal cells (MSCs) are used for prophylaxis of acute graft-versus-host disease (aGvHD) after allogeneic hematopoietic cell transplantation (allo-HCT). Not all samples of MSC are efficient for aGvHD prevention. The suitability of MSCs for aGvHD prophylaxis was studied.

METHODS

MSCs were derived from the bone marrow (BM) of HCT donor and cultivated for no more than three passages. The characteristics of donor BM samples including colony-forming unit fibroblast (CFU-F) concentration, growth parameters of MSCs, and the relative expression levels (REL) of different genes were analyzed. MSCs were injected intravenously precisely at the moment of blood cell reconstitution.

RESULTS

MSCs infusion induced a significant threefold decrease in aGvHD development and improved overall survival compared with the standard prophylaxis group. In ineffective MSC samples (9.4%), a significant decrease in total cell production and the REL of CSF1, FGFR1, and PDGFRB was observed. In all studied BM samples, the cumulative MSC production and CFU-F concentrations decreased with age. The expression levels of FGFR2, PPARG, and VEGF differed by age.

CONCLUSIONS

A universal single indicator for the prediction of MSC eligibility for aGvHD prophylaxis was not identified. A multiparameter mathematical model for selecting MSC samples effective for the prevention of aGvHD was proposed.

Age- and gender-associated changes in the concentrations of serum TGF-1β, DHEA-S and IGF-1 in healthy captive baboons (Papio hamadryas anubis)

Age-related changes in the concentration of factors like TGF-1β, DHEA-S and IGF-1 may increase the risk of disease and illnesses in advanced life. A better understanding of these changes would aid in the development of more appropriate treatments and/or preventative care for many conditions associated with age. Due to their similar immune system and vulnerability to pathogens, baboons are an ideal model for humans. However, little research has been done examining the general effects of age in baboons. Therefore, we wanted to further examine the effects of aging in baboons by determining the age-dependent changes in serum TGF-1β, DHEA-S and IGF-1 concentrations. Blood samples were collected during routine health checks in 113-118 captive baboons. In addition, longitudinal samples from 23 to 27 adult individuals were collected an average of 10.7years apart. Both age and gender influenced the concentrations of serum TGF-1β and IGF-1. When both genders were analyzed together, TGF-1β increased 16.1% as adults, compared to younger and older animals, but male and female baboons showed a slightly different temporal pattern of change. IGF-1 decreased with increasing age and males had a 30% greater concentration of IGF-1 than did females. While there was no effect of gender among our population, serum DHEA-S was negatively correlated with age, decreasing by 51.6% in the oldest animals. There were no effects of age or gender on serum IGFBP-3. In longitudinal samples collected from the same individuals, the concentrations of TGF-1β, DHEA-S and IGF-1 were reduced with age. The results presented herein provide additional knowledge of the aging process in baboons and further validate the use of this species as an appropriate model for aging in humans.

Effect of GH/IGF-1 on Bone Metabolism and Osteoporsosis

Background. Growth hormone (GH) and insulin-like growth factor (IGF-1) are fundamental in skeletal growth during puberty and bone health throughout life. GH increases tissue formation by acting directly and indirectly on target cells; IGF-1 is a critical mediator of bone growth. Clinical studies reporting the use of GH and IGF-1 in osteoporosis and fracture healing are outlined. Methods. A Pubmed search revealed 39 clinical studies reporting the effects of GH and IGF-1 administration on bone metabolism in osteopenic and osteoporotic human subjects and on bone healing in operated patients with normal GH secretion. Eighteen clinical studies considered the effect with GH treatment, fourteen studies reported the clinical effects with IGF-1 administration, and seven related to the GH/IGF-1 effect on bone healing. Results. Both GH and IGF-1 administration significantly increased bone resorption and bone formation in the most studies. GH/IGF-1 administration in patients with hip or tibial fractures resulted in increased bone healing, rapid clinical improvements. Some conflicting results were evidenced. Conclusions. GH and IGF-1 therapy has a significant anabolic effect. GH administration for the treatment of osteoporosis and bone fractures may greatly improve clinical outcome. GH interacts with sex steroids in the anabolic process. GH resistance process is considered.

Somatotropic and thyroid hormones in the acute phase of subarachnoid haemorrhage

BACKGROUND

Somatotropic and thyroid hormones are probably important for the recovery after acute brain injury. Still, the dynamics of these hormones after spontaneous subarachnoid haemorrhage (SAH) is not well described. The purpose of this study was to investigate the relation between somatotropic and thyroid hormones and clinical factors after SAH.

METHODS

Twenty patients with spontaneous SAH were included prospectively. Serum concentrations of TSH, fT4, T3, IGF-1 and GH were measured once a day for 7 days after SAH. Hormone patterns and serum concentrations were compared to the severity of SAH, neurological condition at admission, clinical course and outcome of the patients.

RESULTS

During the first week after SAH, all patients showed increased GH and IGF-1 concentrations. In the whole group, concentrations of TSH increased, whereas T3 and fT4 decreased. There were no relations of serum concentrations of IGF-1 or GH to clinical condition at admission, clinical course or outcome of the patients. Half of the patients showed low T3 serum concentrations. A complicated course was associated with a deeper fall in TSH and T3 concentrations. There were negative correlations for mean concentrations of TSH and T3 versus WFNS grade and a positive correlation for T3 versus GOS after 6 months, indicating that low concentrations of TSH and T3 were connected to worse SAH grade and poor outcome.

CONCLUSIONS

All patients showed increased GH and IGF-1 concentrations irrespective of the grade of SAH or clinical course. Patients with a complicated clinical course showed a more pronounced fall in TSH and T3 concentrations and low serum T3 concentrations were related to a more serious SAH and poor patient outcome. These results need to be studied further and they may contribute to the accumulated knowledge needed to understand the complex mechanisms influencing the unpredictable clinical course after SAH.

Improved prediction of all-cause mortality by a combination of serum total testosterone and insulin-like growth factor I in adult men

OBJECTIVE

Lower levels of anabolic hormones in older age are well documented. Several studies suggested that low insulin-like growth factor I (IGF-I) or testosterone levels were related to increased mortality. The aim of the present study was to investigate the combined influence of low IGF-I and low testosterone on all-cause mortality in men.

METHODS AND RESULTS

From two German prospective cohort studies, the DETECT study and SHIP, 3942 men were available for analyses. During 21,838 person-years of follow-up, 8.4% (n=330) of men died. Cox model analyses with age as timescale and adjusted for potential confounders revealed that men with levels below the 10th percentile of at least one hormone [hazard ratio (HR) 1.38 (95% confidence-interval (CI) 1.06-1.78), p=0.02] and two hormones [HR 2.88 (95% CI 1.32-6.29), p<0.01] showed a higher risk of all-cause mortality compared to men with non-low hormones. The associations became non-significant by using the 20th percentile as cut-off showing that the specificity increased with lower cut-offs for decreased hormone levels. The inclusion of both IGF-I and total testosterone in a mortality prediction model with common risk factors resulted in a significant integrated discrimination improvement of 0.5% (95% CI 0.3-0.7%, p=0.03).

CONCLUSIONS

Our results prove that multiple anabolic deficiencies have a higher impact on mortality than a single anabolic deficiency and suggest that assessment of more than one anabolic hormone as a biomarker improve the prediction of all-cause mortality.

Standardized centile curves and reference intervals of serum insulin-like growth factor-I (IGF-I) levels in a normal Japanese population using the LMS method

Measurements of insulin-like growth factor-I (IGF-I) are useful not only for diagnosis and management of patients with growth hormone (GH)-related disorders but also for assessing nutritional status. We reported population-based references of serum IGF-I in 1996. However, they did not properly reflect data in the transition period from puberty to maturity. The aim of the present study was to re-establish a set of normative data for IGF-I for the Japanese population. The study included 1,685 healthy Japanese subjects (845 males, 840 females) from 0 to 83 years old. Subjects suffering from diseases that could affect IGF-I levels were excluded. Obese or extremely thin adult subjects were also excluded. IGF-I concentrations were determined by commercially available immunoradiometric assays. The reference intervals were calculated using the LMS method. Median IGF-I levels reached 310 ng/mL in males at the age of 14 years and 349 ng/mL in females at the age of 13 years, falling to 124 ng/mL and 103 ng/mL, respectively, by the age of 70 years. The mean pretreatment IGF-1 SD scores in patients with severe GH deficiency (GHD) obtained from the database of the Foundation for Growth Science and from clinical studies for adult GHD were -2.1±1.6 and -4.9±2.5, respectively. The present study established age- and gender-specific normative IGF-I data for the Japanese population and showed the utility of these references for screening patients with severe GHD.

Epidemiologic survey: reference ranges of serum insulin-like growth factor 1 levels in Caucasian adult population with immunoradiometric assay

Gender, age adjusted, population based reference ranges are necessary to use insulin-like growth factor 1 (IGF-1) as a diagnostic marker or for therapeutic monitoring in growth hormone (GH) related diseases. The aim of the present study was to describe the serum IGF-1 distribution and to calculate age and gender specific reference values for Caucasian adult population. A representative sample of 1002 male and 1039 female, totally 2041 participants aged above 18 years old was examined. The subjects suffering from diabetes mellitus, renal diseases, liver diseases, cancer, or diseases of pituitary gland were excluded by medical history, physical examination, and laboratory tests. The subjects were not using any drug that could affect IGF-1 levels. Body mass index (BMI)>30 or<18 kg/m2 were excluded. Serum IGF-1 concentrations were determined by immunoradiometric assay (IRMA). Serum IGF-1 concentrations were declined with age in both males and females after the age of 18. Males had significantly higher serum IGF-1 levels than females in the age groups 18-24, 50-69 (P<0.05), but not in others (P>0.05). The present study established age and gender specific reference ranges for serum IGF-1 levels calculated for Caucasian adult population with IRMA that could be used in medical practice.

Insulin-like growth factor 1 (IGF1), IGF binding protein 3 (IGFBP3), and breast cancer risk: pooled individual data analysis of 17 prospective studies

BACKGROUND

Insulin-like growth factor 1 (IGF1) stimulates mitosis and inhibits apoptosis. Some published results have shown an association between circulating IGF1 and breast-cancer risk, but it has been unclear whether this relationship is consistent or whether it is modified by IGF binding protein 3 (IGFBP3), menopausal status, oestrogen receptor status or other factors. The relationship of IGF1 (and IGFBP3) with breast-cancer risk factors is also unclear. The Endogenous Hormones and Breast Cancer Collaborative Group was established to analyse pooled individual data from prospective studies to increase the precision of the estimated associations of endogenous hormones with breast-cancer risk.

METHODS

Individual data on prediagnostic IGF1 and IGFBP3 concentrations were obtained from 17 prospective studies in 12 countries. The associations of IGF1 with risk factors for breast cancer in controls were examined by calculating geometric mean concentrations in categories of these factors. The odds ratios (ORs) with 95% CIs of breast cancer associated with increasing IGF1 concentrations were estimated by conditional logistic regression in 4790 cases and 9428 matched controls, with stratification by study, age at baseline, and date of baseline. All statistical tests were two-sided, and a p value of less than 0.05 was considered significant.

FINDINGS

IGF1 concentrations, adjusted for age, were positively associated with height and age at first pregnancy, inversely associated with age at menarche and years since menopause, and were higher in moderately overweight women and moderate alcohol consumers than in other women. The OR for breast cancer for women in the highest versus the lowest fifth of IGF1 concentration was 1.28 (95% CI 1.14-1.44; p<0.0001). This association was not altered by adjusting for IGFBP3, and did not vary significantly by menopausal status at blood collection. The ORs for a difference in IGF1 concentration between the highest and lowest fifth were 1.38 (95% CI 1.14-1.68) for oestrogen-receptor-positive tumours and 0.80 (0.57-1.13) for oestrogen-receptor-negative tumours (p for heterogeneity=0.007).

INTERPRETATION

Circulating IGF1 is positively associated with breast-cancer risk. The association is not substantially modified by IGFBP3, and does not differ markedly by menopausal status, but seems to be confined to oestrogen-receptor-positive tumours.

FUNDING

Cancer Research UK.

Lifestyle, anthropometric, and obesity-related physiologic determinants of insulin-like growth factor-1 in the Third National Health and Nutrition Examination Survey (1988-1994)

PURPOSE

Epidemiologic studies suggest that insulin-like growth factor-1 (IGF-1) is associated with obesity and, more recently, cancer. This study investigates multiple lifestyle, physiologic, and anthropometric determinants of circulating IGF-1 concentrations.

METHODS

Nationally representative data were used from the cross-sectional Third National Health and Nutrition Examination (NHANES III, 1988-1994) survey, which measured IGF-1 concentrations in blood, from a subsample of participants who were examined in the morning. After exclusion of persons with missing data, 6,058 men and women 20 years of age or older were included in the study.

RESULTS

The mean IGF-1 concentrations were 260 ng/mL in the entire population and were higher among men as compared with women (278.8 vs. 241.3 ng/mL; p<0.0001). IGF-1 decreased with increasing age (p<0.0001), body mass index (p<0.0001), and waist circumference (p<0.0001). Individuals with metabolic syndrome had lower IGF-1 concentrations after adjustment for covariates (p=0.0008). IGF-1 was inversely associated with increasing number of metabolic syndrome abnormalities (p=0.0008). All associations were stronger among women compared with men except across concentrations of glucose. IGF-1 concentrations did not vary by any other lifestyle or physiologic factors.

CONCLUSIONS

Age, adiposity, hyperglycemia, and metabolic syndrome influenced circulating IGF-1 concentrations. Diet and physical activity had no impact on IGF-1 in this nationally representative population.

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.

Reference ranges of serum IGF-1 and IGFBP-3 levels in a general adult population: results of the Study of Health in Pomerania (SHIP)

OBJECTIVE

Insulin-like growth factor I (IGF-1), which is mostly carried by IGF binding protein 3 (IGFBP-3), mediates endocrine actions of growth hormone and represents an important prognostic factor for systemic diseases. The main objectives of the present study were (1) to calculate age- and sex-specific reference values for serum IGF-1 and IGFBP-3 levels using the Gaussian mean+/-1.96 *standard deviation method and the quantile regression method and (2) to perform a comparison of the results from both statistical methods.

DESIGN

Cross-sectional study (Study of Health in Pomerania). The study population included 2499 men and women aged 20-79 years.

METHODS

Serum IGF-1 and IGFBP-3 levels were determined by chemiluminescence immunoassays. Linear and quantile regressions were performed to calculate age- and sex-related reference ranges.

RESULTS

Both statistical methods generated different results: The reference ranges based on linear regression identified 43 (1.7%) subjects with serum IGF-1 levels and 99 (4.0%) subjects with serum IGFBP-3 levels outside the reference range. Using quantile regression, 117 (4.7%) or 118 subjects (4.7%) with serum IGF-1 or IGFBP-3 levels outside the range were detected, respectively.

CONCLUSION

The present study established age- and sex-specific reference ranges for serum IGF-1 and IGFBP-3 levels. Quantile regression should be preferred to calculate reference ranges because a better concordance to original data is possible due to no distribution assumption are required and the robustness against outliers is given.

Growth hormone decreases visceral fat and improves cardiovascular risk markers in women with hypopituitarism: a randomized, placebo-controlled study

CONTEXT

Data regarding gender-specific efficacy of GH on critical endpoints are lacking. There are no randomized, placebo-controlled studies of physiological GH therapy solely in women.

OBJECTIVE

Our objective was to determine the effects of physiological GH replacement on cardiovascular risk markers and body composition in women with GH deficiency (GHD).

DESIGN

This was a 6-month, randomized, placebo-controlled, double-blind study.

SETTING

The study was conducted at the General Clinical Research Center.

STUDY PARTICIPANTS

43 women with GHD due to hypopituitarism were included in the study.

INTERVENTION

Study participants were randomized to receive GH (goal mid-normal serum IGF-1) or placebo.

MAIN OUTCOME MEASURES

Cardiovascular risk markers, including high-sensitivity C-reactive protein, tissue plasminogen activator, and body composition, including visceral adipose tissue by cross-sectional computed tomography, were measured.

RESULTS

Mean daily GH dose was 0.67 mg. The mean IGF-1 sd score increased from -2.5 +/- 0.3 to -1.4 +/- 0.9 (GH) (P < 0.0001 vs. placebo). High-sensitivity C-reactive protein decreased by 38.2 +/- 9.6% (GH) vs.18.2 +/- 6.0% (placebo) (P = 0.03). Tissue plasminogen activator and total cholesterol decreased, and high-density lipoprotein increased. Homeostasis model assessment-insulin resistance and other markers were unchanged. Body fat decreased [-5.1 +/- 2.0 (GH) vs. 1.9 +/- 1.0% (placebo); P = 0.002] as did visceral adipose tissue [-9.0 +/- 5.9 (GH) vs. 4.3 +/- 2.7% (placebo); P = 0.03]. Change in IGF-1 level was inversely associated with percent change in visceral adipose tissue (r = -0.61; P = 0.002), total body fat (r = -0.69; P < 0.0001), and high-sensitivity C-reactive protein (r = -0.51; P = 0.003).

CONCLUSIONS

Low-dose GH replacement in women with GHD decreased total and visceral adipose tissue and improved cardiovascular markers, with a relatively modest increase in IGF-1 levels and without worsening insulin resistance.

Serum IGF-I measured by four different immunoassays in patients with adult GH deficiency or acromegaly and in a control population

BACKGROUND

IGF-I is a useful tool in GH disorders diagnosis, however, the use of commercially available kits needs to be validated.

OBJECTIVE

To validate the use of serum IGF-I concentrations measured by four immunoassays in the diagnosis of adult GH deficiency and acromegaly.

DESIGN

Cross-sectional study.

PATIENTS

Fifty GH-deficient (GHD) patients, 41 acromegaly patients and 405 controls.

MEASUREMENTS

Serum IGF-I concentrations were measured by four commercial immunoassays: (1) RIA-NICHOLS; (2) ICMA-IMMULITE; (3) IRMA-IMMUNOTECH; and (4) non-extraction-IRMA-DSL. Reference values were established from the control population in six age groups. Individual results were transformed to standard deviation score (SD score) from the age-related reference population and reference data provided by each assay manufacturer. Diagnostic sensitivity for GH deficiency was calculated.

RESULTS

IGF-I measured by the four assays differed significantly. In controls, assay 2 yielded the lowest results, followed by assays 1, 3 and 4 (P < 0.0001 for all comparisons). IGF-I declined with age, but no sex-related differences were observed. When IGF-I was standardized with respect to reference data obtained from the manufacturers, it showed better sensitivity in assays 1 and 2, than with our controls (65%vs. 77.5% and 58%vs. 70%, respectively) for GHD diagnosis. With assays 3 and 4, higher sensitivity was obtained when standardized with our controls (62%vs. 52% and 56%vs. 36%, respectively). In acromegaly, IGF-I was > 2 SD score with all assays.

CONCLUSIONS

IGF-I SD score for GHD diagnosis differed according to the normative data used. All assays proved to be useful for active acromegaly diagnosis.

Normal age-dependent values of serum insulin growth factor-I: results from a healthy Italian population

Serum IGF-I levels were measured in 547 non-hypopituitaric, non-acromegalic healthy subjects of both sexes in Italy to develop reference values in relation to age and sex. Participant subjects were stratified in three age classes (25- 39, 40-59 and >or=60 yr) and IGF-I assay was carried out by double-antibody radio immunoassay. Pearson's correlation coefficient between age and IGF-I values was calculated by sex and predefined age ranges. IGF-I levels significantly decreased with age (p<0.001, Kruskal-Wallis test) while sex was not a significant factor. The median IGF-I levels were 206 ng/ml in the 25-39 yr range, 147 ng/ml in the 40-59 yr range and 103 ng/ml in the >or=60 yr range. Pearson's correlation coefficient confirmed the negative correlation between age and IGF-I levels in the total sample of subjects (r=-0.529). The r coefficient between age and IGF-I levels did not differ between sexes (r=-0.570 in males and r=-0.529 in females), thus reflecting no sex-effect on IGF-I levels decline over years. No correlations were found in the 25-39 yr range (r=-0.036) or in the 40-59 yr range (r=-0.080) either, while in subjects aged >60 yr, IGF-I levels tended to further decrease with increased age (r=0.389). Ranges of normal values set at the 2.5th-97.5th percentile in the three age ranges were 95.6-366.7 ng/ml between 25 and 39 yr, 60.8-297.7 ng/ml between 40 and 59 yr and 34.5-219.8 ng/ml in subjects aged >or=60 yr. This study may contribute to the development of age-specific reference ranges for IGF-I determination in serum of normal subjects of both sexes in Italy.

Regulation of IGF-I function by proinflammatory cytokines: at the interface of immunology and endocrinology

During the past decade, the immune and endocrine systems have been discovered to interact in controlling physiologic processes as diverse as cell growth and differentiation, metabolism, and even human and animal behavior. The interaction between these two major physiological systems is a bi-directional process. While it has been well documented that hormones, including prolactin (PRL), growth hormone (GH), insulin-like growth factor-I (IGF-I), and thyroid-stimulating hormone (TSH), regulate a variety of immune events, a great deal of data have accumulated supporting the notion that cytokines from the innate immune system also affect the neuroendocrine system. Communication between these two systems coordinates processes that are necessary to maintain homeostasis. Proinflammatory cytokines often act as negative regulatory signals that temper the action of hormones and growth factors. This system of 'checks and balances' is an active, ongoing process, even in healthy individuals. Dysregulation of this process has been implicated as a potential pathogenic factor in the development of co-morbid conditions associated with several chronic inflammatory diseases, including type 2 diabetes, cardiovascular disease, cerebrovascular disease, inflammatory bowel disease, rheumatoid arthritis, major depression, and even normal aging. Over the past decade, research in our laboratory has focused on the ability of the major proinflammatory cytokines, tumor necrosis factor (TNF)alpha and interleukin (IL)-1beta, to induce a state of IGF resistance. This review will highlight these and other new findings by explaining how proinflammatory cytokines induce resistance to the major growth factor, insulin-like growth factor-I (IGF-I). We also highlight that IGF-I can induce resistance or reduce sensitivity to brain TNFalpha and discuss how TNFalpha, IL-1beta, and IGF-I interact to regulate several aspects of behavior and cognition.

Serum levels of insulin-like growth factor-I and insulin-like growth factor-I binding protein-3: quality control for studies of stored serum

The insulin-like growth factor (IGF) axis, particularly IGF-I and IGF binding protein-3 (IGFBP-3), has been the subject of much attention because of its role in juvenile growth and their association with cancers at several sites. However, epidemiologic studies of IGF-I and IGFBP-3 have had mixed results and several authors have speculated that quality control (QC), sample storage history, and other methodologic concerns could play a role in this heterogeneity. This article documents the results of storage history and QC efforts for a study of IGF-I and IGFBP-3 in 6,226 serum samples from the National Health and Nutrition Examination Survey III (NHANES III). The study was carried out on site at Diagnostic Systems Laboratories in Webster, Texas, using the IGF-I ELISA (DSL 10-5600) and the IGFBP-3 immunoradiometric assay (DSL 6600). A run-in study of assay performance suggested that plates, days, and weeks significantly affected the variance of both assays. Analysis of samples with different storage histories also indicated strong effects of storage history. Serum samples disbursed to laboratories for measurement of diverse analytes and then returned for storage showed reductions in serum IGF-I level averaging 43% and reductions in IGFBP-3 of 25% compared with samples shipped immediately to the repository for long-term storage at -80 degrees C. Therefore, the main study was carried out using samples that had been shipped directly to the National Center for Health Statistics/NHANES collection center for storage. Laboratory analyses of NHANES III and QC samples were carried out over approximately 10 months. QC was monitored through repeated testing of blood samples from six individuals, with two individuals tested twice on each plate. Assay performance was stable over the entire study and coefficients of variation averaged 2% to 3% within plates and approximately 14% for IGF-I and approximately 11.5% for IGFBP-3 over the entire study. Coefficients of variation varied significantly among individual QC subjects, ranging from 12.3% to 17.6% for IGF-I and 8.9% to 12.8% for IGFBP-3. Based on Levy-Jennings plots, approximately 5% of the plates used for IGF-I in the main study were out of compliance. Finally, location on a plate had small but significant effects on IGF-I level. Together, these results highlight the need for care in large studies of putative biomarkers for cancer risk and illustrate some probable sources of heterogeneity in past epidemiologic studies of the IGF axis and cancer.

Regulation of growth hormone action by gonadal steroids

Sex steroids modulate growth hormone (GH) secretion and action. Estrogen attenuates GH action in a dose- and route-dependent manner by inhibiting GH-regulated endocrine function of the liver. Testosterone amplifies the metabolic action of GH while exhibiting similar but independent effects of its own. The strong modulatory effect of gonadal steroids on GH responsiveness provides insights into the biologic basis of sexual dimorphism in growth, development, and body composition and practical information for the clinical endocrinologist in the treatment of hypopituitary patients.

Modulation of growth hormone action by sex steroids

Growth hormone (GH) is a major regulator of growth, somatic development and body composition. Sex steroids can act centrally by regulating GH secretion and peripherally modulating GH responsiveness. This review addresses data of potential clinical relevance on how sex steroids modulate GH secretion and action, aiming to increase the understanding of sex steroid/GH interactions and leading to improved management of patients. Sex steroids regulate GH secretion directly as well as indirectly through IGF-I modulation. Testosterone stimulates GH secretion centrally, an effect dependent on prior aromatization to oestrogen. Oestrogen stimulates GH secretion indirectly by reducing IGF-I feedback inhibition. Whether oestrogen stimulates GH secretion centrally in females is unresolved. Gonadal steroids modify the metabolic effects of GH. Testosterone amplifies GH stimulation of IGF-I, sodium retention, substrate metabolism and protein anabolism while exhibiting similar but independent actions of its own. Oestrogen attenuates GH action by inhibiting GH-regulated endocrine function of the liver. This is a concentration-dependent phenomenon that arises invariably from oral administration of therapeutic doses of oestrogen, an effect that can be avoided by using a parenteral route. This strong modulatory effect of gonadal steroids on GH responsiveness provides insights into the biological basis of sexual dimorphism in growth, development and body composition and practical information for the clinical endocrinologist. It calls for an appraisal of the diagnostic criteria for GH deficiency of GH stimulation tests, which currently are based on arbitrary cut-offs that do not take into account the shifting baseline from the changing gonadal steroid milieu. In the management of GH deficiency in the hypopituitary female, oestrogen should be administered by a nonoral route. In hypopituitary men, androgens should be replaced concurrently to maximize the benefits of GH. In the general population, the metabolic consequences of long-term treatment of women with oral oestrogen compounds, including selective oestrogen receptor modulators, are largely unknown and warrant study.

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

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

Serum TNF-alpha levels are increased and correlate negatively with free IGF-I in Alzheimer disease

Tumor necrosis factor-alpha (TNF-alpha) and insulin-like growth factor-I (IGF-I) have been involved in the pathogenesis of Alzheimer's disease (AD) as neurotoxic and survival factors, respectively. Recent experimental studies suggest that the signalling pathways of TNF-alpha and IGF-I are functionally interrelated. In order to investigate the possible interaction of TNF-alpha and IGF-I in AD and mild cognitive impairment (MCI), the serum levels of total IGF-I, free IGF-I and TNF-alpha were determined in 141 AD patients, 56 MCI cases and 30 controls. As compared with controls, AD patients showed increased TNF-alpha and decreased IGF-I levels in serum, as well as a significant negative correlation between TNF-alpha and free IGF-I values. MCI patients also exhibited significantly higher TNF-alpha levels than controls. The present results suggest that increased TNF-alpha levels are involved in the pathogenesis of AD and MCI, and might antagonize the neurotrophic activity of IGF-I in these medical conditions. In addition, the combined determination of TNF-alpha and IGF-I might be useful to monitor anti-inflammatory and/or neurotrophic drug effects in AD.

The IGF-I/IGFBP-3 system in gingival crevicular fluid and dependence on application of fixed force

BACKGROUND

During application of orthodontic force on the tooth, various molecular parameters associated with tissue remodeling are changed. IGF-I is a regulatory protein produced during periodontal regeneration. IGF binding proteins-3 (IGFBP-3), a specific IGF-I binding protein, is the major regulatory factor of IGF-I activity.

OBJECTIVES

We tested the hypothesis that changes in the IGF-I/ IGFBP-3 system occur during fixed force application to the tooth and that these changes are detectable in the gingival crevicular fluid (GCF).

METHODS

IGFBP-3 and IGF-I secretion into gingival crevicular fluid (GCF) was analyzed by Western blotting and immunoradiometric assay (IRMA), respectively, in GCF of 6 healthy subjects just prior to and during orthodontics treatment using fixed appliances.

RESULTS

We observed a significant time-dependent decrease of IGFBP-3 content in GCF during orthodontic treatment (4 h and 10 days). Reduction in levels of intact, glycosylated 47 kDa form of IGFBP-3 was associated with its degradation and the appearance of intermediate breakdown products. IGF-I levels were significantly increased 4 h after application of orthodontic force, while they were significantly reduced 10 days after the start of treatment.

CONCLUSIONS

IGFBP-3 secretion into GCF and its molecular structure are modified by the fixed force of orthodontic treatment. Alterations in IGFBP-3 appear to be unrelated to the binding to IGF-I, suggesting an IGF-independent role of this binding protein in tooth movement.