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R Koistinen

Publications and source records attributed to R Koistinen.

At least 55 records · Page 3Linked to original sources
PubMed1995

Structural analysis of the oligosaccharides derived from glycodelin, a human glycoprotein with potent immunosuppressive and contraceptive activities.

Glycodelin, also known as placental protein 14 (PP14) or progesterone-associated endometrial protein (PAEP), is a human glycoprotein with potent immunosuppressive and contraceptive activities. In this paper we report the first characterization of glycodelin-derived oligosaccharides. Using strategies based upon fast atom bombardment and electrospray mass spectrometry we have established that glycodelin is glycosylated at Asn-28 and Asn-63. The Asn-28 site carries high mannose, hybrid and complex-type structures, whereas the second site is exclusively occupied by complex-type glycans. The major non-reducing epitopes in the complex-type glycans are: Gal beta 1-4GlcNAc (lacNAc), GalNAc beta 1-4GlcNAc (lacdiNAc), NeuAc alpha 2-6Gal beta 1-4GlcNAc (sialylated lacNAc), NeuAc alpha 2-6Gal beta 1-4GlcNAc (sialylated lacdiNAc), Gal beta 1-4(Fuc alpha 1-3)GlcNAc (Lewisx), and GalNAc beta 1-4(Fuc alpha 1-3)GlcNAc (lacdiNAc analogue of Lewisx). It is possible that the oligosaccharides bearing sialylated lacNAc or lacdiNAc antennae may manifest immunosuppressive effects by specifically blocking adhesive and activation-related events mediated by CD22, the human B cell associated receptor. Oligosaccharides with fucosylated lacdiNAc antennae have previously been shown to potently block selectin-mediated adhesions and may perform the same function in glycodelin. The potent inhibitory effect of glycodelin on initial human sperm-zona pellucida binding is consistent with our previous suggestion that this cell adhesion event requires a selectin-like adhesion process. This result also raises the possibility that a convergence between immune and gamete recognition processes may have occurred in the types of carbohydrate ligands recognized in the human.

Amino Acid Sequence↗
PubMed1995

Diurnal variation of sex hormone binding globulin and insulin-like growth factor binding protein-1 in women with polycystic ovary syndrome.

OBJECTIVES: The aim of this study was to examine (1) the diurnal variation in SHBG and (2) the inter-relationships of insulin, IGF-I, SHBG and IGFBP-1 over 24 hours in 10 women with anovulatory PCOS and compare them with weight-matched ovulatory controls. PATIENTS AND METHODS: The two groups comprised 10 anovulatory women with PCOS (as defined by clinical, ultrasound and biochemical criteria) and 10 weight matched controls. Serum samples were taken at two-hourly intervals for 24 hours and stored for measurement of SHBG, IGFBP-1, insulin and IGF-I. Differences between the groups were compared using the Wilcoxon ranked paired tests of the individual peak and trough concentrations in each group. The variation in insulin, IGFBP-1 and SHBG concentrations over 24 hours was tested using two-way analysis of variance with the factors time and subject. Spearman's correlation coefficient was calculated from the subjects' median value over 24 hours. RESULTS: The median (interquartile range) body mass index (BMI) was 25.2 (22.2-29.3) in the PCOS group and 24.3 (23.2-25.7) kg/m2 in the control group. Serum testosterone (T) and LH levels were significantly raised in the PCOS group compared to the control group; T 3.8 (2.9-5.6) vs 1.9 (1.9-2.5) nmol/l (P < 0.007) and LH 12 (10-15) vs 4.1 (3.6-4.5) IU/I (P < 0.005) respectively. There was no diurnal variation in SHBG. The median (interquartile ranges) of the peak SHBG concentrations was lower in the PCOS group: 29.4 (14.9-39.4) vs 52.1 (39.4-61) nmol/l in the control group (P < 0.01). The fasting levels of insulin at 0600 h (median (interquartile ranges)) were not significantly different between the groups; 6.6 (5.4-9.8) and 6.2 (1.9-7.6) mU/l, respectively, although the peak median concentrations were significantly different; PCOS 66.1 (50.9-129.2) vs 40 (36.1-74.2) mU/l (P < 0.05). Two-way analysis of variance showed a diurnal variation in insulin concentrations in the control group (P = 0.001) but not in the PCOS group (P = 0.1). The diurnal variation in IGFBP-1 was similar in the two groups but the peak median levels were lower in the women with PCOS 54.9 (22.3-79.2) vs 71.5 (60.5-99.3) micrograms/l (P < 0.03). The decline in IGFBP-1 concentrations correlated with the increase in insulin concentrations. The IGF-I concentrations were similar in the two groups. There was a significant negative correlation between SHBG and insulin (P < 0.05) and between insulin and IGFBP-1 (P < 0.01). CONCLUSION: This study demonstrates that there is no diurnal variation in SHBG concentrations and confirms the finding of a marked diurnal variation in the concentration of IGFBP-1. Women with PCOS who are anovulatory have an abnormal pattern of insulin secretion with an absence of diurnal variation compared to weight matched controls. This provides further evidence of the relative insulin resistance which is independent of weight found in women with anovulatory PCOS. The inverse correlations of insulin concentrations with SHBG and IGFBP-1 support the role of insulin as a possible regulator of the circulating levels of these binding proteins although the difference in the time course of their response makes it unlikely that they are co-regulated.

Circadian Rhythm↗
PubMed1995

Growth delay after liver transplantation in childhood: studies of underlying mechanisms.

After liver transplantation in children, growth is often impaired, but the underlying mechanisms are unknown. Glucocorticoids used for immunosuppression are believed to be partly responsible. After renal transplantation in children, reduced growth hormone (GH) secretion and increased serum insulin-like growth factor-binding protein-3 (IGFBP-3) levels have been reported. We attempted to find endocrine factors predicting growth in 18 prepubertal children followed for more than 1 y (mean 2.4 y) after liver transplantation. Spontaneous and stimulated GH secretion, serum IGF-I, IGFBP-3 concentrations, and endogenous cortisol production were measured. GH secretion was reduced in only two patients. Serum IGF-I concentration was normal, but serum IGFBP-3 was elevated or 1 SD above the mean for age in 62% of the patients. Endogenous cortisol production was reduced in most patients during the first year and improved later in only a few. Growth velocity after transplantation did not correlate with GH secretion, serum IGF-I or IGFBP-3 concentration, or with methylprednisolone dose, but correlated positively with serum basal (rs = 0.44, p < 0.05) and stimulated (rs = 0.53, p < 0.005) cortisol concentration. In conclusion, after liver transplantation 1) the normal pulsatile character of nocturnal GH secretion is sustained, and the GH response to stimulation is reduced in only a few patients; 2) serum IGF-I concentrations are normal; 3) serum IGFBP-3 concentrations are elevated or in the upper part of the normal range in most patients; and 4) endogenous cortisol production is reduced in most patients and correlates positively with growth velocity.

Child↗
PubMed1994

Serum placental protein 14 concentrations are similar in the first trimester pregnancies of women after pituitary down-regulation with a gonadotrophin-releasing hormone agonist and normal cycles with frozen embryo transfers.

Previous studies suggest that, in pregnancies after in-vitro fertilization (IVF) and embryo transfer following pituitary down-regulation with a gonadotrophin-releasing hormone analogue (buserelin) and ovulation induction with human gonadotrophins, the serum placental protein 14 (PP14) concentration is lower than in normally conceived pregnancies. We studied serum PP14 concentrations in two groups of women: (i) in 17 infertile women whose pregnancy followed IVF and embryo transfer using buserelin (long protocol) and human menopausal gonadotrophin for ovulation induction; (ii) in 15 women whose pregnancy followed transfer of frozen-thawed embryos. Similar PP14 concentrations were found in both groups on days 9-10, 14-15 and 70-77 after human chorionic gonadotrophin administration (buserelin, IVF/embryo transfer) or spontaneous luteinizing hormone surge (frozen-thawed embryo transfer). Our results show that PP14 secretion is not compromised by pituitary down-regulation with buserelin in infertile women with functional ovaries.

Buserelin↗
PubMed1994

Uterine endocrinology and paracrinology: insulin-like growth factor binding protein-1 and placental protein 14 revisited.

A large number of proteins and peptides have been identified in the endometrium where they are likely to exert local biological effects. These substances may be enzymes, their inhibitors, proteinases, proteinase inhibitors, hormones, or bioactive peptides with diverse functions. Endometrial function and embryo-endometrial interactions require synchronized actions between endocrine and local factors. As examples of local factors recent studies on the insulin-like growth factor (IGF) system and placental protein 14 (PP14) are reviewed. IGF binding protein-1 (IGFBP-1) and PP14 are products of the secretory phase endometrium: IGFBP-1 is produced by decidualized stromal cells and PP14 by glandular epithelial cells. IGFBP-1 may inhibit the action of IGFs at the endometrial-trophoblastic interphase, and it may also have a role in stromal-epithelial interaction. PP14 has immunosuppressive properties, and recent findings indicate that it may play a part in the fertilization process by inhibiting binding of spermatozoa to the zona.

Carrier Proteins↗
PubMed1994

Prostaglandin F2 alpha stimulates release of insulin-like growth factor binding protein-3 from cultured human granulosa-luteal cells.

Human ovarian follicular fluid contains a number of insulin-like growth factor binding proteins (IGFBP) of which IGFBP-3 is the most abundant. IGFBP-3 synthesis is growth hormone-regulated. We studied the effect of prostaglandin F2 alpha (PGF2 alpha) on IGFBP-3 secretion by cultured human granulosa-luteal cells from follicular aspirates of women participating in an in-vitro fertilization programme. The IGFBP-3 concentration was measured using a specific monoclonal immunofluorimetric assay. Contrary to a previous report on unstimulated follicles, this study demonstrated a positive correlation between follicular fluid IGFBP-3 concentration and follicular size. PGF2 alpha was found to stimulate in a dose-dependent fashion the secretion of IGFBP-3. Significant (P < 0.05) effects were found at PGF2 alpha concentrations of 10(-8), 10(-7) and 10(-6) M. Because IGFBP-3 inhibits progesterone production stimulated by insulin-like growth factor (IGF)-I, the PGF2 alpha-induced stimulation of IGFBP-3 production may be one of the mechanisms whereby PGF2 alpha exerts its luteolytic effect via the IGF system.

Carrier Proteins↗
PubMed1994

Insulin-like growth factor I and insulin-like growth factor binding protein 3 as determinants of blood hemoglobin concentration in healthy subjects.

We studied the serum concentrations of IGF-I, IGF-binding protein 3 (IGFBP-3), and testosterone in relation to blood Hb in 60 healthy prepubertal or early pubertal boys twice, with a 9-mo interval. Serum IGF-I and testosterone levels were measured by RIA, and serum IGFBP-3 was measured by monoclonal immunofluorometric assay. Positive correlations were observed between the concentrations of blood Hb and serum IGF-I at the first examination (r = 0.36, p = 0.008) and Hb and IGFBP-3 at both examinations (r = 0.53, p < 0.001, and r = 0.39, p = 0.003). No association between Hb and testosterone concentrations was found. Our results show that blood Hb is positively correlated to serum IGF-I and IGFBP-3 levels, indicating indirectly the involvement of growth hormone in the regulation of physiologic Hb concentration. Because no association was found between Hb and testosterone concentrations, this may indicate that the role of androgens in erythropoiesis may be different at different stages of puberty. It is concluded that the IGF system may be involved in the rise of Hb level during early puberty.

Adolescent↗
PubMed1994

Overnight secretion pattern of growth hormone, sex hormone binding globulin, insulin-like growth factor-1 and its binding protein in obese and non-obese women with polycystic ovarian disease.

The pathophysiological mechanism underlying polycystic ovarian disease (PCOD) is different in obese and lean women. In obese patients the basic disorder is insulin resistance and hyperinsulinemia. In non-obese women the dominant derangement is a relative excess of luteinizing hormone (LH) and growth hormone (GH) production. The levels of GH, LH, sex hormone binding globulin (SHBG) and insulin-like growth factor binding protein-1 (IGFBP-1) were significantly lower and insulin levels considerably higher in obese PCOD women as compared to their non-obese counterparts. There was, however, no difference in the mean IGF-1 levels found in these two groups. The present study was designed to investigate whether, in addition to the mean levels, the overnight pattern of GH, IGF-1, IGFBP-1 and SHBG differed in obese women with polycystic ovaries as compared to that observed in the non-obese PCOD patients. Eight women with PCOD diagnosed by clinical, sonographic and hormonal means were studied. Four had basal body mass index exceeding 27. Blood samples were collected every 20 min over a period of 8 h, starting at 23:00 h. Twenty-four samples were collected from each patient and examined in one batch for GH, IGF-1, IGFBP-1, SHBG and insulin. The secretion patterns of the above substances during the late night (23:00-03:00 h) and early morning (03:00-07:00 h) hours were examined and compared in obese and non-obese PCOD women. Neither GH nor IGF-1 showed a distinct overnight secretion pattern. The overnight secretion patterns of IGFBP-1 and SHBG were similar in obese and non-obese women--the former showing a constant rising during the night and the latter exhibiting a converse trend. The integrated insulin levels were much higher during the late night as compared to early morning hours in all patients. It is proposed that the specific secretion pattern of IGFBP-1 is not directly dependent on body fat mass but is regulated by insulin in both obese and non-obese patients.

Adult↗
PubMed1994

Different forms of insulin-like growth factor-binding protein-3 detected in serum and seminal plasma by immunofluorometric assay with monoclonal antibodies.

Monoclonal antibodies against recombinant insulin-like growth factor-binding protein-3 (IGFBP-3) were produced to study the various forms of IGFBP-3 and to develop a specific immunofluorometric assay. We tested seven antibodies that showed no cross-reactions with the other five human IGFBPs. By immunoblotting, the main bands in normal serum were seen at > 90, 45, 41, 29, and 25 kDa. In pregnancy serum, the 29-kDa was stronger, and the double band at 41-45 kDa was weaker or totally absent. We characterized two immunofluorometric assays. IGF-I had no effect on either assay. Added IGF-II lowered the amount of recombinant IGFBP-3 measured by the 5C11/7F8 assay, but not by the 1B6/5C11 assay. In normal serum and follicular fluid, IGFBP-3 measurements were lower by the 5C11/7F8 assay, but in most pregnancy sera and amniotic fluids the assays gave similar results. The 5C11/7F8 assay also detected IGFBP-3 in seminal plasma, whereas the 1B6/5C11 assay did not. We conclude that the results of IGFBP-3 measurement depend on the antibodies used, and that different antibodies are suitable for the IGFBP-3 measurement in different body fluids.

Amniotic Fluid↗
PubMed1993

Phosphorylation of insulin-like growth factor-binding protein-1 increases in human amniotic fluid and decidua from early to late pregnancy.

Different fractions of insulin-like growth factor-binding protein-1 (IGFBP-1) from anion exchange chromatography represent differently phosphorylated forms as demonstrated by protein kinase and alkaline phosphatase treatments. The major fraction is non-phosphorylated. Three minor fractions are more phosphorylated and, in native polyacrylamide gel electrophoresis (PAGE), they migrate faster than the major fractions. We studied the changes in phosphorylation of decidual and amniotic fluid IGFBP-1 during pregnancy. Both in decidua and in amniotic fluid the degree of phosphorylation increased from early to late pregnancy, as indicated by faster mobility of IGFBP-1 in native PAGE and increased relative amount of the phosphorylated forms in anion exchange chromatography. The more phosphorylated forms had higher IGF-binding affinity than the less phosphorylated forms. As the degree of phosphorylation of IGFBP-1 is highest in full term decidua it is likely that the inhibitory role of IGFBP-1 is accentuated in the end of pregnancy.

Amniotic Fluid↗
PubMed1993

Polycystic ovaries in non-obese and obese patients: possible pathophysiological mechanism based on new interpretation of facts and findings.

This study was designed to investigate the basic concentrations of different hormones in obese and non-obese patients with polycystic ovarian disease (PCOD). Eight women with PCOD, of whom four were obese with body mass index (BMI, kg/m2) of > 25 and four were non-obese with BMI < 25, volunteered to participate in this study. Serum samples were taken every 20 min over an 8 h period, starting at 2300 h, on day 5 of a spontaneous or gestagen-induced cycle. Basic insulin concentration was found to be significantly higher in the obese women compared with their non-obese counterparts (P < 0.0001). Serum concentrations of insulin-like growth factor binding protein (IGFBP-I) and sex hormone binding globulin (SHBG) were found to be significantly lower (P < 0.001 for both hormones) in the obese compared with the non-obese women. Serum concentrations of insulin-like growth factor I (IGF-I) did not differ between the two groups. The non-obese women had significantly higher serum concentrations of luteinizing hormone (LH) (P < 0.001) and of growth hormone (GH) (P < 0.002) than their obese counterparts. Based on these results, two models of the development of PCOD were suggested. In obese women, hyperinsulinaemia causes an excessive production of androgens through the enhancement of IGF-I receptors which, in synergism with LH, causes increased activity of cytochrome P-450c 17a. In non-obese patients, relative increase of GH concentration stimulates excessive ovarian IGF-I production. At this point synergism with LH results in excessive production of androgens by the same mechanism as in obese patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Response of sex hormone binding globulin and insulin-like growth factor binding protein-1 to an oral glucose tolerance test in obese women with polycystic ovary syndrome before and after calorie restriction.

OBJECTIVE: We determined the relationship of short-term changes in circulating insulin concentrations, resulting from an oral glucose load, to those in both sex hormone binding globulin (SHBG) and insulin-like growth factor binding protein 1 (IGFBP-1) and assessed the effect of a short-term low calorie diet on the levels of SHBG and IGFBP-1 during an oral glucose tolerance test. DESIGN: A within-group comparison of biochemical indices during an oral glucose tolerance test before and after calorie restriction. PATIENTS AND METHODS: Six obese women with polycystic ovary syndrome with mean (SD) BMI 34.2 (3.4) kg/m2 were studied before and after one month on a very low calorie diet (350 kcal/day; Cambridge diet). Each subject was given a 75-g oral glucose load after an overnight fast and blood samples were taken every 30 minutes for 3 hours. These were analysed for glucose, insulin, SHBG, and IGFBP-1. RESULTS: All the women lost weight (range 1.7-9.5 kg). The SHBG concentrations did not change significantly during the oral glucose tolerance test but there was a highly significant decline in IGFBP-1 levels both before (0 min, mean (SD) 27.3 (10.6); 180 min, 8.9 (4.2) micrograms/l) and after (0 min, 28.4 (12.1); 180 min, 6.2 (2.1) micrograms/l, P < 0.001) dieting. The sum of the SHBG concentrations during the test, however, was significantly lower prior (129.9 (40.5) nmol/l) to calorie restriction than after (164.3 (70.6) nmol/l), whereas there was no significant effect of dieting on the IGFBP-1 response to glucose. CONCLUSIONS: The changes in insulin and SHBG concentrations found after dieting have been confirmed. SHBG levels, in contrast to IGFBP-1, do not change in response to a short-term increase in insulin or glucose concentrations. The difference in the response of the two binding proteins may be explained by differences in their half-lives in the circulation or the regulation of mRNA for the peptides by insulin. This study confirms that insulin regulates both SHBG and IGFBP-1 but that there is a difference in the time course of the response of the two proteins to insulin.

Carrier Proteins↗
PubMed1993

Insulin-like growth factor-I (IGF-I) inhibits production of IGF-binding protein-1 while stimulating estradiol secretion in granulosa cells from normal and polycystic human ovaries.

We have investigated the actions of FSH and insulin-like growth factor-I (IGF-I) on the production of IGF-binding protein-1 (IGFBP-1) by granulosa cells from unstimulated normal and polycystic (PCO) human ovaries and related these effects to those on estradiol (E2). IGFBP-1 concentrations were measured in granulosa cell-conditioned medium (48-h culture with 10(-7) M testosterone) and follicular fluid. IGF-I (50 ng/mL), in the absence of FSH, stimulated E2 production by granulosa cells from both normal and polycystic ovaries, and there was a synergistic action between IGF-I and FSH. Granulosa cells secreted IGFBP-1 in concentrations ranging from 20-500 pg/1000 cells.48 h, with cells from two of four normal and three of four polycystic ovaries showing a dose-related increase in IGFBP-1 production in response to FSH. In contrast, the addition of as little as 100 pg/mL IGF-I to cells incubated with testosterone or testosterone plus FSH, caused complete inhibition of IGFBP-1 production. FSH treatment produced the expected dose-related increase in E2 accumulation. IGFBP-1 was detectable in fluid from all sizes of follicle tested, but there was no correlation of IGFBP-1 concentrations with follicle size and no difference between normal and polycystic ovaries. These data indicate that IGFBP-1 and E2 are differentially regulated by IGF-1 in the human ovary.

Carrier Proteins↗
PubMed1993

Tri-iodothyronine and cycloheximide enhance insulin-like growth factor-binding protein-1 gene expression in human hepatoma cells.

The growth-regulating actions of IGFs are modulated by their binding proteins (IGFBPs). The serum concentration of IGFBP-1 is down-regulated by insulin, and in-vitro studies have demonstrated that IGFBP-1 secretion from various tissues and cells can be stimulated by theophylline, forskolin, oestrogen and progesterone. We have studied the effects and mechanisms of thyroid hormone action on IGFBP-1 gene expression and secretion by human hepatoma cells in vitro. Tri-iodothyronine dose-dependently enhanced IGFBP-1 secretion in serum-free HepG2 cell cultures after 24-48 h of exposure, as measured by a specific immunofluorometric assay. This was accompanied by an increase (+ 50%) in the amount of IGFBP-1 mRNA, which could be prevented by cycloheximide, a protein synthesis inhibitor. Cycloheximide transiently enhanced (+ 200%) the accumulation of IGFBP-1 mRNA at 3-12 h of incubation, when no effect of tri-iodothyronine was observed. It is concluded that thyroid hormone stimulates IGFBP-1 secretion slowly by enhancing IGFBP-1 gene expression by a protein mediator. The acute stimulation of IGFBP-1 gene transcription by cycloheximide associates this gene with a number of growth-related genes encoding growth- and tumour-associated peptides.

Carrier Proteins↗
PubMed1993

Phosphorylation of insulin-like growth factor-binding protein-1 from different sources.

During purification, insulin-like growth factor binding protein-1 from amniotic fluid was separated into five different peaks by anion exchange chromatography. These peaks represent differently phosphorylated forms of IGFBP-1. The major peak (peak 1) is non-phosphorylated. Peaks 3, 4, and 5 are more phosphorylated and, in native polyacrylamide gel electrophoresis (PAGE), they migrate faster than peaks 1 and 2. The more phosphorylated forms have higher IGF-I-binding affinity. Both dephosphorylated and phosphorylated peaks enhanced IGF-I stimulated DNA-synthesis in fetal skin fibroblast cell culture. They, however, inhibited the binding of IGF-I to the same cells. The phosphorylation of IGFBP-1 was changed during pregnancy. In decidua and in amniotic fluid the degree of phosphorylation increased from early to late pregnancy, as indicated by faster mobility of IGFBP-1 in native PAGE and increased relative amount of the more phosphorylated peaks in anion exchange chromatography. Human ovarian follicular fluid, culture media from human granulosa cells and endometrial adenocarcinoma cells (HEC-1-B) consisted mostly of the non-phosphorylated form of IGFBP-1.

Amniotic Fluid↗
PubMed1992

The effect of endocrine therapy with medroxyprogesterone acetate, 4-hydroxyandrostenedione or tamoxifen on plasma concentrations of insulin-like growth factor (IGF)-I, IGF-II and IGFBP-1 in women with advanced breast cancer.

Tamoxifen treatment of women with advanced breast cancer has previously been reported to reduce plasma insulin-like growth factor-type I (IGF-I) concentrations. In this study we have examined the effect of treatment with Tamoxifen, medroxyprogesterone acetate (MPA) or 4-hydroxyandrostenedione (4-OHA) on plasma IGF-I and IGF-II concentrations. As IGF-binding proteins (IGFBPs) can modulate the biological effects of IGF-I, plasma IGFBP-I levels were also measured. Treatment with Tamoxifen for 2 weeks resulted in a small, but significant, decrease in IGF-I levels, but increase in the plasma concentration of IGFBP-I. In contrast, treatment with MPA increased levels of IGF-I, but significantly reduced plasma IGFBP-I concentrations. Treatment with 4-OHA had no significant overall effect on plasma IGF-I or IGFBP-I levels, although changes were detected for some subjects. Plasma IGF-II concentrations were not altered by treatment with Tamoxifen, MPA or 4-OHA. It is concluded that although treatment with Tamoxifen or MPA produced significant changes in plasma IGF-I concentrations, any physiological effects of such changes are likely to be modulated by the corresponding alterations in plasma IGFBP-I concentrations.

Aged↗
PubMed1992

The effect of estrogen level on glucose-induced changes in serum insulin-like growth factor binding protein-1 concentration.

OBJECTIVE: To investigate the regulation of insulin-like growth factor binding protein-1 (IGFBP-1) concentration during ovarian stimulation. DESIGN: A prospective study of patients undergoing in vitro fertilization treatment. SETTING: Infertility unit at the University Central Hospital of Oulu, a tertiary referral center. PATIENTS: Sixteen healthy, regularly menstruating lean tubal infertility patients. INTERVENTIONS: Oral glucose tolerance test was performed first in a hypoestrogenic state after suppression by long-term gonadotropin-releasing hormone (GnRH) agonist and, second, in a hyperestrogenic state after stimulation by human menopausal gonadotropins. MAIN OUTCOME MEASURES: Serum concentrations of IGFBP-1, insulin-like growth factor I (IGF-I), insulin and sex hormone-binding globulin were measured before and 2 hours after glucose administration. RESULTS: Before and after glucose administration, the serum IGFBP-1 concentrations were significantly higher in the hyperestrogenic state (estradiol [E2] level 3.5 +/- 0.57 nmol/L) after ovarian stimulation than in the GnRH-analogue-induced hypoestrogenic state before the gonadotropin treatment (E2 level 0.10 +/- 0.02 nmol/L). On both occasions glucose-induced hyperinsulinemia caused a significant decrease in the circulating IGFBP-1 levels, whereas the IGF-I levels remained unchanged. There was a significant correlation between E2 and the insulin-suppressed IGFBP-1 level. The sum of follicular diameters correlated positively with the serum IGFBP-1 concentration. CONCLUSIONS: Gonadotropin-induced hyperestrogenism is related to elevated serum IGFBP-1 levels, either via estrogen-stimulated synthesis or via increased contribution from multiple follicles. Glucose-induced hyperinsulinemia suppresses serum IBFBP-1 concentration equally both in the hypoestrogenic and hyperestrogenic states. Because of similar IGF-I levels, it is likely that the biological activity of IGF-I is different before and after gonadotropin stimulations.

Adult↗