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Query: UMLS:C0432222 (SEM)
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Serum insulin-like growth factor II (IGF-II) was characterized by radioimmunoassay and Western immunoblot in 44 patients with non-islet cell tumor hypoglycemia (NICTH). 31 of 44 patients with NICTH had big IGF-II in sera. When the presence of IGF-II in tumors from 20 patients was investigated, IGF-II in tumors was detected in 18 patients and these patients had big IGF-II in sera. In two patients whose tumors did not contain IGF-II, big IGF-II in sera was not detected. In six patients with IGF-II in tumors, hypoglycemia disappeared and the big IGF-II decreased after successful removal of the tumors. These data indicate that the big IGF-II could be related to hypoglycemia, and that the increased serum big IGF-II suggests IGF-II-producing NICTH. Serum IGF-II levels in 31 patients with big IGF-II were greater than those in 13 patients without it (Mean +/- SEM: 723+/-54 vs. 326+/-31 ng/ml), but the elevated IGF-II levels were found in only 13 patients. Serum IGF-I levels were low in all patients with NICTH. In the 13 patients without big IGF-II, serum IGF-II levels were lower than those in the patients with big IGF-II, and serum IGF-I levels were also low. Serum IGF-II/IGF-I ratios in the patients with big IGF-II were elevated and greater than those in the patients without big IGF-II (35.0+/-2.2 vs. 11.5+/-2.4). The present data indicate that IGF-II-producing tumors are not rare in NICTH, and serum big IGF-II and IGF-II/IGF-I ratio are useful for screening patients with IGF-II-producing NICTH.
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PMID:Serum insulin-like growth factor II in 44 patients with non-islet cell tumor hypoglycemia. 979 Feb 31

Despite recent interest in the therapeutic potential of recombinant human insulin-like growth factor-I (rhIGF-I) in the treatment of diabetes mellitus, its mechanism of action is still not defined. We have studied the effects of low-dose bolus subcutaneous rhIGF-I (40 microg/kg and 20 microg/kg) on insulin sensitivity, growth hormone (GH) and glucagon levels in seven young adults with insulin-dependent diabetes mellitus (IDDM) using a randomized double-blind placebo-controlled crossover study design. Each was subjected to a euglycemic clamp (5 mmol/L) protocol consisting of a variable-rate insulin infusion clamp (6:00 PM to 8:00 AM) followed by a two-dose hyperinsulinemic clamp (insulin infusion of 0.75 mU x kg(-1) x min(-1) from 8 to 10 AM and 1.5 mU x kg(-1) x min(-1) from 10 AM to 12 noon) incorporating [6,6 2H2]glucose tracer for determination of glucose production/utilization rates. Following rhIGF-I administration, the serum IGF-I level (mean +/- SEM) increased (40 microg/kg, 655 +/- 90 ng/mL, P < .001; 20 microg/kg, 472 +/- 67 ng/mL, P < .001; placebo, 258 +/- 51 ng/mL). Dose-related reductions in insulin were observed during the period of steady-state euglycemia (1 AM to 8 AM) (40 microg/kg, 48 +/- 5 pmol/L, P = .01; 20 microg/kg, 58 +/- 8 pmol/L, P = .03; placebo, 72 +/- 8 pmol/L). The mean overnight GH level (40 microg/kg, 9.1 +/- 1.4 mU/L, P = .04; 20 microg/kg, 9.6 +/- 2.0 mU/L, P = .12; placebo, 11.3 +/- 1.7 mU/L) and GH pulse amplitude (40 microg/kg, 18.8 +/- 2.9 mU/L, P = .04; 20 microg/kg, 17.0 +/- 3.4 mU/L, P > .05; placebo, 23.0 +/- 3.7 mU/L) were also reduced. No differences in glucagon, IGF binding protein-1 (IGFBP-1), acetoacetate, or beta-hydroxybutyrate levels were found. During the hyperinsulinemic clamp conditions, no differences in glucose utilization were noted, whereas hepatic glucose production was reduced by rhIGF-I 40 microg/kg (P = .05). Our data demonstrate that in subjects with IDDM, low-dose subcutaneous rhIGF-I leads to a dose-dependent reduction in the insulin level for euglycemia overnight that parallels the decrease in overnight GH levels, but glucagon and IGFBP-1 levels remain unchanged. The decreases in hepatic glucose production during the hyperinsulinemic clamp study observed the following day are likely related to GH suppression, although a direct effect by rhIGF-I cannot be entirely discounted.
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PMID:Effects of low-dose recombinant human insulin-like growth factor-I on insulin sensitivity, growth hormone and glucagon levels in young adults with insulin-dependent diabetes mellitus. 986 78

The molecular basis for GH resistance in chronic renal failure is unknown. It may partly reside in a decreased number of hepatic GH receptors and subsequently reduced IGF-I synthesis. To investigate the hepatic expression of GH receptor/binding protein (GHBP) and IGF-I genes in chronic renal failure, mRNA levels and the concentrations of its splicing variants were measured by Northern Blot in male 5/6 nephrectomized rats (NX, n = 9), aged 26 +/- 1 days, and three groups of sham-operated rats: (1) fed ad libitum (SAL, n = 9); (2) pair-fed with NX (SPF, n = 7); and (3) pair-fed with NX in terms of protein ingestion but calorically supplemented up to the intake of SAL (SPF+, n = 8). NX rats had severe renal failure, serum urea nitrogen 106 +/- 11 mg/dl (mean +/- SEM), and were growth retarded. GH receptor/GHBP gene expression was detected as two bands of 4.7 and 1.2 kb, respectively. The amount of mRNA was lower (P < 0.0001) in NX than SAL, either when both bands were considered together or separately. No differences were found between NX, SPF, and SPF+. Serum GHBP concentrations were higher (P < 0.01) in NX rats than the other groups. For the IGF-I gene, two bands of 7.5 and 1.8-0.8 kb were identified. Expression of IGF-I gene was reduced (P < 0.05) in NX in comparison with SAL, this reduction being more marked for the 7.5 kb transcript (amount of mRNA equal to 56.6 +/- 2.6 vs 84.8 +/- 6.2% of values found in SAL rats). There were no differences between NX and SPF. Normalization of caloric intake in SPF+ resulted in partial recovery of the 7.5-kb band and did not modify the 1.8-0.8 kb mRNAs. Circulating IGF-I levels were no different among the four groups. These data confirm that expression of liver GH receptor/GHBP and IGF-I genes is markedly decreased in uremic rats. Nutritional deficiency and not uremia itself seems to be the main causal factor, with protein deficit playing a major role.
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PMID:Hepatic expression of growth hormone receptor/binding protein and insulin-like growth factor I genes in uremic rats. Influence of nutritional deficit. 1020 9

Despite the discovery of potent GH-releasing peptides (GHRPs) more than 15 yr ago and the recent cloning of human, rat, and pig GHRP receptors in the hypothalamus and pituitary gland, the neuroregulatory mechanisms of action of GHRP agonists on the human hypothalamo-somatotroph unit are not well delineated. To gain such clinical insights, we evaluated the ultradian (pulsatile), entropic (pattern orderliness), and nyctohemeral GH secretory responses during continuous 24-h i.v. infusion of saline vs. the most potent clinically available hexapeptide, GHRP-2 (1 microg/kg x h) in estrogen-unreplaced (mean serum estradiol, 12 +/- 2.4 pg/mL) postmenopausal women (n = 7) in a paired, randomized design. Blood was sampled every 10 min for 24 h during infusions and was assayed by ultrasensitive GH chemiluminescence assay. Pulsatile GH secretion was quantitated by deconvolution analysis, orderliness of GH release patterns by the approximate entropy statistic, and 24-h GH rhythmicity by cosinor analysis. Statistical analysis revealed that GHRP-2 elicited a 7.7-fold increase in (24-h) mean serum (+/-SEM) GH concentrations, viz. from 0.32 +/- 0.042 (saline) to 2.4 +/- 0.34 microg/L (GHRP-2; P = 0.0006). This occurred via markedly stimulated pulsatile GH release, namely a 7.1-fold augmentation of GH secretory burst mass: 0.87 +/- 0.18 (control) vs. 6.3 +/- 1.3 microg/L (GHRP-2; P = 0.0038). Enhanced GH pulse mass reflected a commensurate 10-fold (P = 0.023) rise in GH secretory burst amplitude [maximal GH secretory rate (micrograms per L/min) attained within a secretory pulse] with no prolongation in event duration. GH burst frequency, interpulse interval, and calculated GH half-life were all invariant of GHRP-2 treatment. Concurrently, as detected in the ultrasensitive GH assay, GHRP-2 augmented deconvolution-estimated interpulse (basal) GH secretion by 4.5-fold (P = 0.025). The approximate entropy of 24-h serum GH concentration profiles rose significantly during GHRP-2 infusion; i.e. from 0.592 +/- 0.073 (saline) to 0.824 +/- 0.074 (GHRP-2; P = 0.0011), signifying more irregular or disorderly GH release patterns during secretagogue stimulation. Cosinor analysis of 24-h GH rhythms disclosed a significantly earlier (daytime) acrophase at 2138 h (+/- 140 min) during GHRP-2 stimulation vs. 0457 h (+/-42 min) during saline infusion (P = 0.013). Concomitantly, the cosinor amplitude rose 6-fold (P = 0.018), and the mesor (cosine mean) rose 5-fold (P = 0.003). Fasting (0800 h) plasma insulin-like growth factor (IGF-I) concentrations rose by -11 +/- 12 microg/L during saline infusion and by 102 +/- 18 microg/L during GHRP-2 infusion (P = 0.0036). GHRP-2 infusion did not modify (24-h pooled) serum LH, FSH, or TSH concentrations and minimally increased serum (pooled) daily PRL (6.8 +/- 0.83 vs. 12 +/- 1.2 microg/L; P < 0.05) and cortisol (5.3 +/- 0.59 to 7.0 +/- 0.74; P < 0.05) concentrations. In summary, 24-h constant iv GHRP-2 infusion in the gonadoprival female neurophysiologically activates the GH-IGF-I axis by potentiating GH secretory burst mass and amplitude by 7- to 10-fold and augmenting the basal (nonpulsatile) GH secretion by 4.5-fold. GHRP-2 action is highly selective, as it does not alter GH secretory burst frequency, interpulse interval, event duration, or GH half-life. GHRP-2 effectively elevates IGF-I concentrations, unleashes greater disorderliness of GH release patterns, and heightens the 24-h rhythmicity of GH secretion. These tripartite features of GHRP-2's action in estrogen-withdrawn (postmenopausal) women also characterize normal human puberty and/or sex steroid regulation of the GH-IGF-I axis. However, how or whether GHRP-2 interacts further with sex hormone modulation of GH neurosecretory control in older women and men is not yet known.
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PMID:Tripartite neuroendocrine activation of the human growth hormone (GH) axis in women by continuous 24-hour GH-releasing peptide infusion: pulsatile, entropic, and nyctohemeral mechanisms. 1037 23

In a randomized cross-over study in five healthy males we compared 75-min constant i.v. infusion of saline, low-dose recombinant human (rh) insulin-like growth factor-I (rhIGF-I; 1.5 microg/kg/h) and high-dose rhIGF-I (9.0 microg/kg/h). Serum samples were analysed for ultrafiltered free IGF-I (fIGF-I), total IGF-I (tIGF-I), tIGF-II and IGF-binding protein-1 (IGFBP-1) and -3. Free and total IGF-I were unchanged during saline infusion. Low-dose rhIGF-I caused a small increment in fIGF-I [+41%, from 0.64 +/- 0.19 (mean +/- SEM) to 0.90 +/- 0.25 microg/l;P< 0.05] and tIGF-I (+9%, from 220 +/- 31 to 239 +/- 33 microg/l;P< 0.05). High-dose rhIGF-I increased tIGF-I by 40% (from 227 +/- 36 to 329 +/- 31 microg/l;P< 0.05), and fIGF-I by 11.5 times (from 0.56 +/- 0.20 to 6.46 +/- 1.39 microg/l;P< 0.05). The pharmacokinetic profile of fIGF-I was calculated after high-dose IGF-I only. The disappearance of fIGF-I followed first order kinetics with an apparent half-life of 14.4 +/- 1.0 [11.2-17.1 (range)] min. The clearance was estimated to 52 +/- 20 (16-128) ml/min/kg and the volume of distribution to 1102 +/- 464 (388-2899) ml/kg. In the three experiments, there were no differences in IGFBP-1, and tIGF-II and IGFBP-3 remained unchanged. In conclusion, fIGF-I remained within the physiological range after low-dose rhIGF-I, whereas high-dose rhIGF-I resulted in supraphysiological concentrations. Since the half-life estimates for each subject were remarkably similar, this parameter most likely does not explain the observed variation in clearance and volume of distribution of fIGF-I. Instead, differences in the circulating and cellular IGF-I binding capacity may be of importance.
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PMID:The pharmacokinetics of free insulin-like growth factor-I in healthy subjects. 1037 48

Serum IGF-I levels were measured in 14 patients (9 children and 5 adults) with Laron syndrome (LS) during long-term treatment by IGF-I. Recombinant IGF-I (FK-780, Fujisawa Pharmaceutical Co. Ltd., Japan) was administered once daily subcutaneously before breakfast for 3-5 years to the children and for 9 months to the adults. The initial daily dose was 150 micrograms/kg for children and 120 micrograms/kg for adults. Before initiation of treatment the mean overnight fasting levels of serum IGF-I in the children was 3.2 +/- 0.8 nmol/l (mean +/- SEM), rising to 10 +/- 1.7 nmol/l during long-term treatment even on a dose of 120 micrograms/kg/day. The serum IGF-I levels 4 hours after injection rose from 31.2 +/- 3.5 to 48 +/- 2 nmol/l. In the adult patients, the initial basal IGF-I was 4.1 +/- 0.7 nmol/l, rising to 16.1 +/- 3.84 nmol/l after 8-9 months treatment. Serum IGF-I levels at 4 hours after injection rose in the adult patients from 24.1 +/- 5.8 up to 66.8 +/- 15.4 nmol/l. A progressively increasing half-life during long term exogenous administration of IGF-I to patients with Laron syndrome was demonstrated by following serum IGF-I dynamics after injection. Based on the fact that no antibodies to IGF-I were detected and on findings in previous studies, it is speculated that the increasing serum IGF-I levels during long-term IGF-I treatment are caused by an increase in serum IGFBP-3 induced by chronic IGF-I administration. It is concluded that treatment with IGF-I necessitates regular monitoring of serum IGF-I levels; in patients in whom the age adjusted maximal levels are exceeded, a reduction of the daily IGF-I dose is indicated to avoid undesirable effects.
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PMID:Serum insulin-like growth factor-I (IGF-I) levels during long-term IGF-I treatment of children and adults with primary GH resistance (Laron syndrome). 1039 60

Several observations suggest that GH stimulates sebaceous gland growth and development. Therefore, we studied the effects of GH and insulin-like growth factors (IGFs), alone and with androgen, on sebaceous epithelial cell (sebocyte) growth and differentiation in vitro. The rat preputial cell culture model system was used to judge differentiation (induction of lipid-forming colonies, LFCs) and DNA synthesis. GH increased sebocyte differentiation. At a dose of 10(-8) M in the presence of micromolar insulin, GH was 3.8 times more potent than IGF-I (38.1+/-4.2%, SEM, vs. 10+/-1.5% LFCs) and 6 times more potent than IGF-II (6+/-0.5% LFCs). IGF-I 10(-8) M alone stimulated a similar amount of differentiation as insulin 10(-6) M, although it was less effective than insulin in augmenting the effect of GH on differentiation. GH had no effect on sebocyte uptake of 3H-thymidine at doses up to 10(-6) M. On the other hand, IGF-I was the most potent stimulus of DNA synthesis (168% of control; P < 0.001 vs. all others). IGF-II 10(-8) M stimulated 3H-thymidine incorporation similarly to insulin 10(-6) M. In the presence of insulin, dihydrotestosterone (DHT) 10(-6) M induced 31.4+/-1.7% LFCs, and there was a tendency of DHT and GH to interact in promoting differentiation. When insulin was omitted from the system, differentiation was decreased overall, but GH +/- DHT slightly improved differentiation. The IGFs had no effect on the response to DHT. DHT decreased DNA synthesis by 40%, an effect unaltered by GH or IGFs. These results suggest that GH and IGFs have different functions in sebaceous cell growth and differentiation: GH stimulated differentiation beyond that found with IGFs or insulin, yet had no effect on DNA synthesis, a parameter stimulated most potently by IGF-I. While GH augmented the effect of DHT on differentiation, the IGFs had no effect on the response of DHT. These data indicate that GH may in part act directly on sebocytes rather than indirectly through IGF production. These data are consistent with the concept that increases in GH and IGF production contribute in complementary ways to the increase in sebum production during puberty and in acromegaly.
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PMID:Growth hormone and insulin-like growth factors have different effects on sebaceous cell growth and differentiation. 1046 80

Polycystic ovary syndrome (PCOS) is the most common cause of anovulation in women. Previous studies suggest that the pathogenesis of PCOS may involve interrelated abnormalities of the insulin-like growth factor (IGF) and ovarian steroidogenesis systems. We investigated this hypothesis in fasting serum samples from 140 women with PCOS (age, 27.4 +/- 0.4 yr; body mass index, 26.3 +/- 0.5 kg/m2; mean +/- SEM). IGF-related parameters were also studied in a group of normoovulatory women (n = 26; age, 26 +/- 4 yr; body mass index, 23.6 +/- 4.3 kg/m2). For the PCOS group, the mean testosterone (T) level was 2.5 +/- 0.1 nmol/L, and it was significantly correlated with LH (r = 0.41; P < 10(-6)), estrone (r = 0.33; P = 0.016), estradiol (r = 0.18; P = 0.04), and androstenedione (AD; P < 10(-6)), but not with dehydroepiandrosterone sulfate (P = 0.71), a marker of adrenal steroidogenesis. T and AD were also related to total ovarian follicle number and ovarian size, as previously found with normoovulatory women (1). There were no differences between the PCOS subjects and the normoovulatory group for total IGF-I, IGF-II, or IGF-binding protein-3 (IGFBP-3). However, IGFBP-1 levels were significantly decreased in the PCOS group (1.0 +/- 0.2 vs. 7.3 +/- 1.1 ng/mL; P < 0.001) and were inversely correlated with serum insulin levels (r = -0.50; P < 10(-8)). Serum levels of free IGF-I (fIGF-I) were elevated (5.9 +/- 0.3 vs. 2.7 +/- 0.3 ng/mL; P < 0.001) in inverse relation with IGFBP-1 (r = -0.31; P = 0.046). Serum fIGF-I levels were related to total follicle number (r = - 0.35; P < 10(-4)) and to the ratio of sex hormone-binding globulin to T (r = -0.23; P = 0.009). However, these relationships were not independent of other variables. Despite the more than 2-fold elevation in fIGF-I levels, significant relationships between fIGF-I and markers of ovarian steroidogenesis (T, AD, estradiol, and estrone) could not be demonstrated. In conclusion, although we confirmed correlations between LH and hyperandrogenemia and have found abnormalities in the IGF system in a large cohort of PCOS subjects, a direct relationship between hyperandrogenism and the IGF system could not be shown. Previous studies suggest that elevated LH and hyperinsulinemia lead to excess ovarian androgen synthesis in PCOS and that the intraovarian IGF system is important for normal follicle development and may be important in the arrested state of follicle development in PCOS. However, the data presented in this cross-sectional study suggest that insulin-related changes in circulating IGFBP-1 and subsequent elevation of fIGF-I reflect insulin resistance and have little enhancing effects on ovarian steroidogenesis in this disorder.
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PMID:Elevated serum levels of free insulin-like growth factor I in polycystic ovary syndrome. 1048 60

Aim of the present study was to further clarify the negative GH auto-feedback mechanisms in childhood. To this goal we studied the effects of rhGH and/or GHRH administration on the GH response to GHRH or hexarelin (HEX), a peptidyl GH secretagogue, in normal short children. In 34 prepubertal children (12 girls and 22 boys, age 8.2- 14.2 yr) with normal short stature (normal height velocity and IGF-I levels) the following tests were performed: group A (no.=11): GHRH (GHRH 1 - 29, Geref, Serono; 1 microg/kg iv at 150 min) preceded by saline or GHRH at 0 min; group B (no.=6): GHRH preceded by saline or rhGH (0.005 IU/kg iv at 0 min); group C (no.=6): GHRH preceded by rhGH alone or combined with GHRH; group D (no.=6): HEX (2 microg/kg iv at 150 min) alone or preceded by rhGH. In group A, the GH response to GHRH was not modified by pre-treatment with GHRH (GH peak, mean+/-SEM: 16.7+/-2.9 vs 15.1+/-2.3 microg/l, respectively). In group B, the GH response to GHRH was clearly inhibited by rhGH (8.7+/-2.3 vs 38.8+/-4.5 microg/l, p<0.001); the GH rise after rhGH in group B overlapped with that after GHRH in group A. In group C, the GH response to GHRH after pre-treatment with rhGH (13.2+/-4.0 microg/l) was similar to that in group B and was not significantly modified by pre-treatment with rhGH+ GHRH (6.9+/-2.7 microg/l); the GH rise after rhGH+GHRH was higher (p<0.05) than that after rhGH alone. In group D, the GH response to HEX was significantly blunted by pre-treatment with rhGH (34.1+/-11.7 vs 51.2+/-17.9 microg/l, p<0.05). Our results demonstrate that in childhood the somatotroph response to GHRH is preserved after GHRH while it is inhibited after rhGH administration, which is also able to blunt the GH response to HEX. Thus, the somatostatin-mediated negative GH auto-feedback is already operative in childhood; the reason why the GHRH- induced GH rise is not inhibited by GHRH pre-treatment is unexplained.
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PMID:The negative GH auto-feedback in childhood: effects of rhGH and/or GHRH on the somatotroph response to GHRH or hexarelin, a peptidyl GH secretagogue, in children. 1080 72

To determine breed differences in ovarian function and endocrine secretion, daily rectal ultrasonography was conducted on multiparous lactating Angus (temperate Bos taurus; n = 12), Brahman (tropical Bos indicus; n = 12), and Senepol (tropical Bos taurus; n = 12) cows during an estrous cycle in summer. Blood was collected daily to quantify plasma concentrations of FSH, LH, progesterone, estradiol, GH, insulin-like growth factor (IGF)-I, IGF-II, IGF binding proteins (IGFBP), insulin, glucose, and plasma urea nitrogen (PUN). Numbers of small (2 to 5 mm), medium (6 to 8 mm), and large follicles (> or = 9 mm) were greater (P < .05) in Brahman than in Angus and(or) Senepol cows. Length of the estrous cycle (SEM = .6 d) was similar (P > .10) among Senepol (20.4 d), Angus (19.5 d), and Brahman (19.7 d) cows. Senepol cows had greater (P < .05) diameters of the corpus luteum (CL) and a delayed regression of the CL as compared with Angus cows. The secondary surge of FSH (between d 1 and 2; d 0 = estrus) was greater in Angus than Brahman or Senepol cows (breed x day, P < .05). Between d 2 and 14 of the estrous cycle, concentrations of progesterone, LH, IGF-II, and binding activities of IGFBP-3, IGFBP-2, and the 27- to 29-kDa IGFBP in plasma did not differ (P > .10) among breeds. Concentrations of GH, IGF-I, insulin, and PUN were greater (P < .001) and binding activities of the 22-kDa and 20-kDa IGFBP tended (P < .10) to be greater in plasma of Brahman than in Angus or Senepol cows. Plasma glucose concentrations were greater (P < .05) in Senepol than in Brahman or Angus cows. In conclusion, Brahman (Bos indicus) and Senepol cows (tropical Bos taurus) had greater numbers of follicles in all size categories and greater diameter of CL than Angus (temperate Bos taurus) cows. These ovarian differences may be due to changes in the pattern of secretion of FSH, insulin, IGF-I, and GH but not LH, IGF-II, or IGFBP-2 or -3.
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PMID:Ovarian and endocrine characteristics during an estrous cycle in Angus, Brahman, and Senepol cows in a subtropical environment. 1083 85


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