Importance of cannulated prolactin test in the definition of hyperprolactinaemia.

PURPOSE: Recent guidelines suggest that a single prolactin measurement is adequate to confirm hyperprolactinaemia. This may lead to unnecessary investigation of artefactual hyperprolactinaemia. Prolactin measurement drawn from an indwelling cannula after rest removes stress as a confounding variable. The objective was to determine the frequency of true hyperprolactinaemia amongst patients referred following a single prolactin measurement. METHODS: A cannulated study was considered if prolactin on referral ('Referral Prolactin') was <5,500 mU/L (260 ng/mL) but >410 mU/L (19 ng/mL) in males or >510 mU/L (24 ng/mL) in females, irrespective of clinical context. Case-notes of 267 patients undergoing cannulated prolactin measurement over a 10-year period (2000-2010) were reviewed. Pre-existing pituitary disease, dopamine antagonist use, and macroprolactinaemia were excluded. Morning ante-cubital vein cannulation was followed immediately by withdrawal of 'Repeat Prolactin' sample. After 120-min bed-rest, 'Resting Prolactin' was withdrawn through the cannula. RESULTS: 235 patients were included for analysis. 64 (27%) were within normal range; following Repeat Prolactin in 41 (17%) and Resting Prolactin in 23 (9%) cases. Referral Prolactin was higher in patients with true hyperprolactinaemia, 1,637 ± 100 mU/L (77.2 ± 4.7 ng/mL) than with artefactual hyperprolactinaemia, 1,122 ± 68 mU/L (52.9 ± 3.2 ng/mL; P < 0.001) but there was substantial overlap. 21 out of 171 cases (12%) with true hyperprolactinaemia had a macroadenoma. Presenting symptoms did not predict true hyperprolactinaemia. Referral Prolactin of 2,000 mU/L (94 ng/mL) had 97% specificity to identify true hyperprolactinaemia. CONCLUSIONS: Reliance on a single, non-rested prolactin value may lead to over-diagnosis of hyperprolactinaemia. A resting sample should be considered with random values <2,000 mU/L (94 ng/mL).

Dysregulation of the insulin/IGF binding protein-1 axis in transgenic mice is associated with hyperinsulinemia and glucose intolerance.

The insulin/IGF binding protein-1 (IGFBP-1) axis is important in coordinating insulin- and IGF-mediated regulation of glucose metabolism and glycemia. Dysregulation of the axis may play a role in the pathophysiology of disorders of insulin deficiency and resistance. We have investigated this hypothesis by generating transgenic mice that overexpress hIGFBP-1. To study the axis in its true physiological context, we used a human (h) IGFBP-1 cosmid clone so that transgene expression is responsive to normal hormonal stimuli. hIGFBP-1 mRNA is expressed in a tissue-specific fashion, and measurement of serum protein levels by specific immunoassay indicates normal physiological regulation in response to fasting/feeding and appropriate post-translational modification as indicated by the detection of phosphorylated and nonphosphorylated isoforms of the protein. The hypoglycemic response to exogenous IGF-I is attenuated in transgenic mice. Transgenic mice exhibit an enhanced insulin secretory response to a glucose challenge, although basal and stimulated blood glucose levels are similar to controls. There is a sexual dimorphism in phenotypic expression: male transgenic mice had higher stimulated glucose and insulin levels than did females. Transgenic mice exhibit fasting hyperglycemia and hyperinsulinemia and glucose intolerance in later life, indicating an age-related decline in glucocompetence. These findings demonstrate the importance of the normal inverse relationship between serum insulin and IGFBP-1 levels in glucoregulation and that sustained dysregulation of the insulin/IGF-I/IGFBP-1 axis is associated with impaired glucose tolerance and abnormalities of insulin action.

Influence of thyroid hormones on the GH-IGF-I axis.

There is a complex relationship between thyroid hormones, GH, and the insulin-like growth factors (IGFs). Thyroid hormones act at many sites from the hypothalamic control of GH release to the tissue expression of IGF-I and its binding proteins (IGFBPs). In this review, we present current knowledge of the effects of altered thyroid status on the GH-IGF-I axis, concentrating on the changes seen in IGF-I gene expression and circulating levels of GH and IGFBPs.

Dexamethasone treatment in man induces changes in 24-hour growth hormone (GH) secretion profile without altering total GH released.

Glucocorticoids inhibit growth in man and laboratory animals and reduce the GH response to the majority of exogenously administered stimuli. Recently, however, glucocorticoids have been shown to have varying effects on GH secretion depending on the time of administration and, furthermore, to be potent secretagogues in their own right. To investigate this further, we have carried out sampling over two 24-h periods in six normal male volunteers both before and directly after treatment with dexamethasone (DEX; 2 mg twice daily) for 96 h. After DEX administration, all volunteers showed an increase in mean GH secretion during the first 9 h of sampling (0900-1800 h) compared with pre-DEX control profiles (5.1 +/- 1.2 vs. 1.7 +/- 0.5 micrograms/L; P less than 0.001). DEX treatment also had the effect of delaying and attenuating the nocturnal peak; mean GH secretion between 0000-0200 h was significantly greater before DEX (13.6 +/- 2.7 micrograms/L) than after DEX (3.6 +/- 0.7 micrograms/L; P less than 0.001), whereas that between 0300-0800 h was greater after DEX (5.5 +/- 0.8 vs. 0.7 +/- 0.2 micrograms/L; P less than 0.001). Individual nocturnal peaks ranged from 7.0-56.8 micrograms/L, occurring between 0030-0200 h before DEX, and 2.6-21.2 micrograms/L, occurring between 0300-0400 h after DEX. Overall mean GH secretion was not significantly altered by DEX treatment (3.8 +/- 0.6 vs. 4.2 +/- 0.5 micrograms/L; P = NS). Total insulin-like growth factor-I (IGF-I) levels, measured after acid-ethanol extraction, were significantly increased by DEX treatment, with mean IGF-I over the 24-h sampling period rising from 292.2 +/- 31.8 to 425.9 +/- 37 micrograms/L (P less than 0.005). All individuals showed an increase in mean 24-h IGF-I of between 10-75%. In a second study, 12 male volunteers were treated with DEX in an identical manner, and blood was taken at 0800 h daily. Total IGF-I levels rose steadily from 307.9 +/- 13.3 micrograms/L, reached a plateau at 72 h and remained elevated at 96 h (424.9 +/- 16.5 micrograms/L; P less than 0.001). These results suggest that glucocorticoids alter the normal pattern of GH secretion with an increase in daytime levels, but a delaying and attenuating effect on the nocturnal pulse. Previous studies have suggested that IGF-I concentrations are decreased by steroid treatment, but these have been based on bioassay systems. Total IGF-I, measured by RIA, would appear to be consistently elevated; the apparent decrease seen in bioassay systems may be due to glucocorticoid-induced changes in binding protein concentrations.

Effects of dexamethasone on growth hormone (GH)-releasing hormone, arginine- and dopaminergic stimulated GH secretion, and total plasma insulin-like growth factor-I concentrations in normal male volunteers.

In man, glucocorticoid treatment and endogenous corticosteroid excess generally suppress stimulated GH release. However, such effects are not entirely consistent and depend on both the duration of pituitary exposure to steroids and the secretagogue employed. To further evaluate the effects of glucocorticoids in man, we have studied the response to four different GH stimulation tests before and after treatment with dexamethasone (DEX; 2 mg twice daily during 84 h). Twelve healthy male volunteers were divided into two groups of six subjects (groups A and B). Group A underwent stimulation tests with arginine (500 mg/kg, i.v.) and GH-releasing hormone (GHRH, 100 micrograms, i.v.) before and after DEX treatment. Group B were subjected to stimulation tests with two dopaminergic agents, a novel nonergot D2-dopamine agonist CV205-502 (CV; 10 micrograms, i.v.) and dopamine (4 micrograms/kg.min, i.v.), before and after DEX. Within each group, the effect of DEX on the different secretagogues was studied 4 weeks apart. GHRH-stimulated GH release was significantly blunted by DEX treatment [median peak GH value, 34.2 micrograms/L; 25-75th percentiles, 22.1-56.2), control, vs. 19.8 (9.7-34.5), DEX; P less than 0.05; integrated GH secretion expressed as the area under the curve (AUC) was 48% lower after DEX; P less than 0.01]. In the same group, DEX treatment significantly enhanced the response to arginine [10.6 (8.0-22.8), control, vs 26.1 (15.1-38.6), DEX; P less than 0.01; with an increase in AUC of 72%; P less than 0.01]. In group B, under control conditions before glucocorticoid administration, the GH response to CV was significantly greater than that to dopamine in terms of both peak response [25.1 (8.6-30.9), CV, vs. 11.8 (5.5-16.4), dopamine; P less than 0.05] and AUC [2406 +/- 654 (CV) vs. 658 +/- 125 (dopamine); P less than 0.01], suggesting that CV may be a useful adjunct in the diagnosis of GH deficiency. After DEX administration, responses to both dopaminergic agents were suppressed [CV, 6.7 (4.0-21.2); P less than 0.01 vs. control response; and dopamine, 5.3 (4.8-7.9); P less than 0.05 vs. control response]. When compared with the effects of dexamethasone on the GH response to arginine, the results with dopaminergic agents highlight important differences in the mechanisms of action of these indirectly acting GH secretagogues. Moreover, this may be of physiological importance, because in contrast to the inhibitory effect of glucocorticoid on GHRH-stimulated GH release, DEX treatment significantly increased basal plasma GH levels [1.4 (0.5-5.1) vs. control 0.3 (0.1-0.6) microgram/L; P less than 0.001].(ABSTRACT TRUNCATED AT 400 WORDS)

Stimulation of growth hormone release in man by the potent D2-dopamine agonist CV 205-502: comparison of responses to intravenous and oral administration.

It is well known that dopaminergic agents are stimulators of GH release in man, and although responses are sometimes unreliable, oral L-dopa and iv dopamine have frequently been employed in the evaluation of GH-deficient states. To assess the effects on GH secretion of a new potent D2-dopamine agonist, the octahydrobenzo(g)quinoline CV 205-502 (CV) we have investigated the GH responses in healthy male volunteers to four different iv doses. For this purpose 3 separate groups of 9 subjects were studied. The respective groups were administered on separate occasions 10 micrograms CV and placebo (group 1), 5 micrograms, 2.5 micrograms, and placebo (group 2), and 1 microgram and placebo (group 3). Each subject received drug and placebo in a double blind randomly assigned order, with at least 5 days between their administration. Active compound or placebo was infused over 30 min, and blood sampling was carried out for 72 h after cessation of infusion. Peak GH levels occurred between 45-60 min after the end of the infusion; the observed maximum GH concentrations were 19.2 +/- 2.9 micrograms/L (10 micrograms, iv; P less than 0.001 vs. placebo), 9.61 +/- 2.1 (5 micrograms, iv; P less than 0.001 vs. placebo), 4.7 +/- 1.7 (2.5 micrograms, iv; P less than 0.05 vs. placebo), and 1.9 +/- 0.8 micrograms/L (1 micrograms, iv; P = NS vs. placebo). The mean integrated GH secretion expressed in arbitrary units [area under the response curve (AUC)] up to 3 h postinfusion showed a typical dose-response relationship. Mean values were 1715 +/- 269.4 (10 micrograms, iv; P less than 0.001 vs. placebo), 956.1 +/- 189.9 (5 micrograms, iv; P less than 0.001 vs. placebo), 312.8 +/- 105.8 (2.5 micrograms, iv), and 162.8 +/- 47.5 (1 microgram, iv). In a second study with a separate group of 18 volunteers, we compared the GH response to an oral dose of 100 micrograms CV with those to 5 micrograms CV given iv and placebo treatment. Peak GH values in this study were 20.3 +/- 5.5 micrograms/L (100 micrograms, orally; P less than 0.01 vs. placebo) and 14.6 +/- 2.8 (5 micrograms, iv; P less than 0.001 vs. placebo). Maximum levels occurred 45 min after the infusion and 90 min after ingestion (60 min relative to the end of the infusion).(ABSTRACT TRUNCATED AT 400 WORDS)

Integrity of the growth hormone/insulin-like growth factor system is maintained in patients with chronic fatigue syndrome.

GH deficiency states and chronic fatigue syndrome (CFS) share several characteristics, and preliminary studies have revealed aspects of GH dysfunction in CFS. This study assessed indexes of GH function in 37 medication-free CFS patients without comorbid psychiatric illness and 37 matched healthy controls. We also assessed GH function before and after treatment with low dose hydrocortisone, which has been shown recently to reduce fatigue in CFS. We measured basal levels of serum insulin-like growth factor I (IGF-I), IGF-II, IGF-binding protein-1 (IGFBP-1), IGFBP-2 and IGFBP-3 together with 24-h urinary GH excretion. We also performed 2 dynamic tests of GH function: a 100-microg GHRH test and an insulin stress test using 0.15 U/kg BW insulin. There were no differences between patients and controls in basal levels of IGF/IGFBP or in urinary GH excretion. GH responses to both the GHRH test and the insulin stress test were no different in patients and controls. CFS patients did have a marginally reduced suppression of IGFBP-1 during the insulin stress test. Hydrocortisone treatment had no significant effect on any of these parameters. There is no evidence of GH deficiency in CFS. At the doses used, hydrocortisone treatment appears to have little impact on GH function.

The effect of short stature, portal hypertension, and cholestasis on growth hormone resistance in children with liver disease.

Chronic liver disease is associated with GH resistance, which is characterized by high circulating GH and low insulin-like growth factor I (IGF-I) concentrations. Standard GH replacement has no effect on serum IGF-I in pediatric liver disease. The aims were to examine whether GH resistance can be overcome by supraphysiological GH and to determine whether GH resistance worsens with the progression of liver disease. Thirty children, divided into five groups whose liver disease was at clinically different stages, were studied. They were given 0.2 IU/kg x day GH for 4 days and then 0.4 IU/kg x day for the next 4 days. Serum IGF-I and binding proteins (IGFBPs) were measured by immunoassay. IGF-I was lower in all study groups than in normal controls. IGF-I, IGFBP-3, and acid-labile subunit rose in response to GH. The magnitude of the response reflected nutritional status and liver dysfunction; in particular, portal hypertension was associated with a poor IGF-I response. There was no change in IGFBP-2. GH resistance begins early in the natural history of childhood liver disease and develops with the progression of liver disease, particularly with portal hypertension. It may be partially overcome by supraphysiological GH administration, but the effect becomes smaller with worsening liver disease.

Reversible effects of cessation and recommencement of thyroxine treatment on insulin-like growth factors (IGFs) and IGF-binding proteins in patients with total thyroidectomy.

There is a complex relationship between the thyroid and pituitary GH/insulin-like growth factor (IGF) axes. IGFs circulate in association with six specific high affinity binding proteins (IGFBPs) that modulate their bioactivity and bioavailability. Recent evidence suggests that gene expression and circulating levels of IGFBPs are related to prevailing thyroid hormone status. We have investigated the effects of both withdrawal and reinstitution of thyroid hormone replacement on circulating IGF and IGFBP levels in athyreotic patients (n = 10). The mean IGF-I concentration fell from a basal level of 191.8 +/- 12 micrograms/L to a nadir of 136.4 +/- 17.8 micrograms/L (P = 0.026) 5 weeks after stopping T4 treatment and returned to normal values 3 weeks after recommencement of replacement treatment. The fall in IGF-II levels followed a similar pattern from a basal mean level of 649 +/- 33.7 to 547 +/- 42.7 micrograms/L (P = 0.026) at 5 weeks. These changes paralleled the fall in free T3 and free T4. Similarly, IGFBP-1 levels fell after stopping T4 treatment from a basal level of 54.8 +/- 4.0 to 24.6 +/- 7.0 micrograms/L (P = 0.001) 5 weeks later. After T4 treatment was restarted, IGFBP-1 levels rose and were not significantly different from basal values by week 8. There were strong positive correlations between paired data sets for IGFBP-1 and free T3 (r = 0.488; P = 0/0037) and free T4 (r = 0.56; P = 0.0006), and a strong negative correlation with TSH (r = -0.515; P = 0.0001). Insulin is known to be important in the regulation of IGFBP-1, but no changes in fasting insulin levels during T4 withdrawal were noted, and levels of IGFBP-1 did not exhibit the normal inverse relationship with circulating insulin levels. Levels of IGFBP-2, assessed by Western ligand blotting, increased during the development of hypothyroidism, peaked 5 weeks after stopping T4 replacement, and declined on reinstitution of replacement treatment. A further level of regulation of the IGF-IGFBP axis is afforded by the presence of specific circulating IGFBP proteases. Proteases directed against IGFBP-3 proteolytically cleave the major carrier BP in the circulation and reduce its binding affinity, possibly resulting in increased tissue IGF bioavailability. Despite the marked reduction in circulating IGF levels and the generation of significant biochemical hypothyroidism, IGFBP-3 protease activity was not apparent during the 10-week period of the study.(ABSTRACT TRUNCATED AT 400 WORDS)

Serum insulin-like growth factor-binding protein-3 (IGFBP-3) levels and IGFBP-3 protease activity in normal, abnormal, and multiple human pregnancy.

Proteolytic activity directed against insulin-like growth factor (IGF)-binding protein-3 (IGFBP-3) is found in human pregnancy serum. We have investigated changes in this protease activity in pregnancies in which the fetus is small for gestational age and in multiple pregnancies. Maternal serum was obtained from 18 singleton pregnancies at 27 weeks gestational age (GA), and matched fetal serum was collected by cordocentesis. Fetuses were appropriate for GA (AGA; n = 6), small for gestational age (SGA) with evidence of uteroplacental insufficiency (UPI; starved SGA; n = 6), or SGA without UPI (nonstarved SGA; n = 6). In a second study, serum was obtained from women with singleton (n = 10), twin (n = 10), and higher multiple pregnancies (n = 10) at 9 weeks GA. All women with more than three fetuses underwent embryo reduction to 2 fetuses before 15 weeks gestation, when a second serum sample was obtained. Circulating IGF-I and IGF-II were measured by RIA, and IGFBP-3 was measured by both RIA and immunoradiometric assay. IGFBP-3 protease activity was assessed by Western ligand blotting after incubation with a normal nonpregnancy sera pool, immunoblotting, and specific protease assay. In the growth study, circulating maternal IGF-I and IGFBP-3 levels were not different in the three groups, but fetal IGF-I and IGFBP-3 levels were significantly lower in the UPI fetuses (IGF-I, 6.9 +/- 0.5 micrograms/L; IGFBP-3, 547 +/- 70 micrograms/L) than in either the nonstarved SGA fetuses (IGF-I, 27.8 +/- 6.3; IGFBP-3, 769 +/- 41 micrograms/L; P < 0.01) or the AGA fetuses (IGF-I, 39.4 +/- 3.4; IGFBP-3, 872 +/- 91 micrograms/L; P < 0.01). Maternal serum IGFBP-3 protease activity, measured by protease using [125I]IGFBP-3 as substrate, was increased in pregnancies complicated by UPI compared with GA-matched pregnancies in which the fetus was AGA or nonstarved SGA. No significant fetal serum protease activity was demonstrated. In the multiple pregnancies, IGFBP-3 rose significantly from 9-15 weeks GA in singleton (P = 0.005), twin (P = 0.004), and multiple (P = 0.007) pregnancies, and levels were higher in mothers of multiple pregnancies than in those of twin (P < 0.05) or singleton (P < 0.01) pregnancies at both 9 and 15 weeks GA. IGF-I levels were not different in the three groups and did not significantly increase between 9-15 weeks GA.(ABSTRACT TRUNCATED AT 400 WORDS)

Sequential changes in insulin-like growth factor I (IGF-I) and IGF-binding proteins in children with end-stage liver disease before and after successful orthotopic liver transplantation.

Pediatric end-stage liver disease (ESLD) leads to poor linear growth and wasting. After orthotopic liver transplantation (OLT), catch-up growth occurs unpredictably and with a delay. The bulk of circulating insulin-like growth factor I (IGF-I) and its major circulating binding protein, IGF-binding protein-3 (IGFBP-3), is derived from the liver. We hypothesized that growth failure in ESLD, both before and after OLT, may result from abnormalities in the IGF-IGFBP axis. Serum IGF-I, IGFBP-1, and insulin were measured by RIA, and IGFBP-3 was determined by immunoradiometric assay in 26 children with ESLD (mean of 3.7 samples pre-OLT and 4.2 samples post-OLT per patient) and 30 age-matched controls. In addition, serum IGFBPs were visualized by Western ligand blotting. IGFBP-3 and IGFBP-2 were also observed by immunoblotting with specific antisera. IGFBP-3 protease activity was determined by protease gels using recombinant human IGFBP-3 label as substrate. Anthropometric measurements were performed according to standard techniques. Pre-OLT, IGF-I (32.7 +/- 4.8 micrograms/L), and IGFBP-3 (1.11 +/- 0.10 mg/L) were significantly lower than control values [IGF-I, 168.3 +/- 16.5 micrograms/L (P = 0.0001); IGFBP-3, 2.57 +/- 0.17 mg/L (P = 0.0001)]. Post-OLT, IGF-I (179.2 +/- 19.7 micrograms/L; P = NS) rose to control levels, whereas IGFBP-3 (3.49 +/- 0.14 mg/L; P = 0.002) became significantly greater than the control value. IGFBP-1 was significantly higher pre-OLT (78.9 +/- 9.6 micrograms/L; P = 0.0001) than post-OLT (45.7 +/- 6.9 micrograms/L), and both were significantly higher than control values (18.5 +/- 2.5 micrograms/L; P = 0.0001 vs. pre-OLT and P = 0.0002 vs. post-OLT). There was a trend toward higher insulin levels both pre-OLT (15.5 +/- 1.8 mU/L) and post-OLT (12.5 +/- 1.4 mU/L) compared with control values (9.7 +/- 1.1 mU/L; P = 0.06 vs. pre-OLT). IGFBP-1 was negatively correlated with serum insulin post-OLT (P = 0.008), but there was no correlation pre-OLT. Western ligand blotting confirmed the changes in IGFBP-3 pre- and post-OLT. Immunoblotting demonstrated a reduction in all mol wt forms of IGFVBP-3 pre-OLT. Protease assays demonstrated the appearance of IGFBP-3 proteolysis only at a time coincidental with the operative stress of OLT; overall, there was no difference in protease activity pre- and post-OLT. IGFBP-2 was unchanged post-OLT compared with pre-OLT, although levels were higher than control values. Mid-upper arm circumference and triceps skin fold thickness SD score 3 months post-OLT and weight SD score 1 yr post-OLT were significantly higher than those at OLT. In conclusion, IGF-I and IGFBP-3 are reduced, and IGFBP-1 and IGFBP-2 are increased in children with ESLD. After OLT, IGF-I levels return to normal, but marked abnormalities in IGFBPs remain. These changes may help to explain at least in part the growth failure seen in pediatric ESLD both before and after successful OLT.

Effects of hypothyroidism and hyperthyroidism on insulin-like growth factors (IGFs) and growth hormone- and IGF-binding proteins.

Normal thyroid status is a prerequisite for the normal growth and development of many tissues. The interrelationships between the thyroid and pituitary-GH-insulin-like growth factor (IGF) axes are complex and not yet fully understood. We have studied the effects of hypothyroidism (n = 22) and hyperthyroidism (n = 17) on levels of serum immunoreactive IGF-I and II, IGF-binding proteins (IGFBP-1 and -3), and IGF bioactivity before and during treatment. We have also assessed changes in GH-binding activity (GHBP). Mean immunoreactive (IR) IGF-I levels in the hypothyroid group rose from 106.6 +/- 10.6 micrograms/L at diagnosis to 139.9 +/- 12.7 micrograms/L (P = 0.009) on normalization of thyroid function. In hyperthyroidism, mean IGF-I levels (258.9 +/- 33.9 micrograms/L) were high initially and fell to 188.7 +/- 14.8 micrograms/L (P = 0.04) after treatment. IR IGF-I levels correlated positively with free T3 and free T4 and negatively with TSH levels. Mean serum IGF-II levels were low in hypothyroid patients (375.2 +/- 37.3) and rose during treatment (516.9 +/- 59.4 micrograms/L; P = 0.04). In the hyperthyroid subjects, however, there was no significant change during therapy (625.0 +/- 66.9 vs. 621.9 +/- 120.8 micrograms/L; P = 0.98). IGF bioactivity potency ratios were low in the hypothyroid group (0.26 +/- 0.03 U/mL) and rose to 0.71 +/- 0.10 U/mL (P = 0.01) during treatment. IGF bioactivity in the hyperthyroid group was also low (0.38 +/- 0.05 U/mL) and rose significantly during treatment (0.81 +/- 0.06 U/mL; P = 0.003). Mean IGFBP-1 levels (29.8 +/- 5.7 micrograms/L) were unaltered by treatment of hypothyroid subjects (28.4 +/- 4.8 micrograms/L). In contrast, IGFBP-1 levels in the hyperthyroid subjects were high at diagnosis (134.6 +/- 26.6 micrograms/L) and fell significantly (71.3 +/- 14.3 micrograms/L; P = 0.04) during treatment. In the hypothyroid group, IGFBP-3 levels rose from an initial mean of 1.98 +/- 0.17 to 2.67 +/- 0.27 mg/L (P = 0.04) during treatment. The higher mean pretreatment levels in the thyrotoxic group (3.46 +/- 0.32 mg/L) were unaltered by treatment (3.20 +/- 0.51 mg/L; P = 0.71). GHBP was low in the hypothyroid group at diagnosis (28.5 +/- 2.5%) and rose during treatment to 40.6 +/- 3.9% (P = 0.02). We have confirmed that IR IGF-I levels are low in hypothyroidism and have demonstrated a reduction in IGF bioactivity and IGF-II and IGFBP-3 levels, and low GH-binding activity, which may reflect a reduction in the processing of GH receptors.(ABSTRACT TRUNCATED AT 400 WORDS)

Cirrhotic liver expresses low levels of the full-length and truncated growth hormone receptors.

In cirrhosis, as in other conditions of protein catabolism, there is a state of acquired GH resistance, as defined by high circulating GH levels with low insulin-like growth factor I levels. However, patients with end-stage liver failure respond to supraphysiological doses of GH with an increase in circulating insulin-like growth factor I levels. The present study represents a detailed analysis of GH receptor (GHR) expression in cirrhotic liver from 17 patients with end-stage liver disease. Specific binding of labeled GH was identified in all cirrhotic livers studied. The binding affinity for the GHR was similar in cirrhotic and normal livers, but the number of binding sites per mg protein of liver membrane was variable in both normal and cirrhotic liver, although it were generally lower in cirrhotic liver. GHR expression was identified in cirrhotic liver by Northern blotting, RT-PCR, and ribonuclease protection assay. On Northern blotting, a single transcript of 4.8 kb was identified in normal and cirrhotic tissues. RT-PCR identified expression of both full-length GHR and a truncated form of the GHR; this was confirmed by ribonuclease protection assay. In situ hybridization and immunohistochemistry confirmed the expression of GHR in regenerating hepatocytes and isolated cells in fibrous tissue. In conclusion, 1) the low level of GHR in cirrhotic liver may contribute to the acquired GH resistance found in cirrhotic patients; 2) the reduced expression of both full-length and truncated GHR is compatible with the low level of GH-binding protein found in cirrhosis, as this truncated receptor has previously been reported to generate large amounts of GH-binding protein; and 3) the demonstration of GH binding to cirrhotic liver explains why these patients with GH resistance may still respond to supraphysiological doses of GH.

The maternal insulin-like growth factor (IGF) and IGF-binding protein response to trisomic pregnancy during the first trimester: a possible diagnostic tool for trisomy 18 pregnancies.

Many lines of evidence point to an important role for the insulin-like growth factors (IGFs) in embryonic and fetal growth in human pregnancy. The bioavailability of IGFs is modulated by IGF-binding proteins (IGFBP-1 to -6), whose permissive or inhibitory actions are regulated in part by posttranslational modification. In second and third trimester pregnancies, maternal IGFBP-1 is elevated in preeclampsia and intrauterine growth retardation. In the first trimester, trisomic pregnancies result in derangement of maternal serum levels of peptides, including hCG beta and pregnancy-associated plasma protein A. Trisomy 18 is characterized by growth failure in the first trimester, whereas trisomy 21 is not; thus, if maternal serum levels of IGFs and IGFBPs reflect fetal growth, changes specific to trisomy 18 may be expected. We report maternal serum levels of IGF-I, IGF-II, and IGFBP-1,-2, and -3; IGFBP-1 phosphorylation; and IGFBP-3 proteolysis in pregnancies (n = 139) complicated by trisomy 18 or trisomy 21 compared with those in normal controls. Maternal IGF-I, IGF-II, and IGFBP-3 showed no significant difference between fetuses with a normal karyotype and those with trisomy 18 or 21. The mean IGFBP-1 level was significantly higher and the mean IGFBP-2 level was lower in fetuses with trisomy 18 compared with normal fetuses [108.8 +/- 6.1 vs. 36.7 +/- 1.9 micrograms/L (P = 0.0001) and 81.2 +/- 5.5 vs. 206.1 +/- 10.2 micrograms/L (P = 0.0001), respectively]. There was no significant difference between the trisomy 21 and normal groups. The reduction in IGFBP-2 was confirmed by Western ligand and immunoblotting, and there was no evidence of variation in lower mol wt products to suggest differential proteolysis. IGFBP-1 phosphoforms and IGFBP-3 proteolysis were not significantly different between groups. The finding of altered maternal serum levels of IGFBP-1 and IGFBP-2 specific to pregnancies complicated by trisomy 18 suggests that these binding proteins may be important mediators of fetal growth in the first trimester, and the clear differences in the ratio of IGFBP-1 to -2 may serve as an additional diagnostic marker for trisomy 18 pregnancies.

Changes in growth hormone, insulin, insulinlike growth factors (IGFs), and IGF-binding protein-1 in chronic fatigue syndrome.

Chronic fatigue syndrome (CFS) is characterized by severe physical and mental fatigue of central origin. Similar clinical features may occur in disorders of the hypothalamopituitary axis. The aim of the study was to determine whether patients with CFS have abnormalities of the growth hormone/insulinlike growth factor (GH-IGF) axis basally or following hypothalamic stimulation with insulin-induced hypoglycemia. We compared levels of GH, IGF-I, IGF-II, IGF-binding protein-1 (IGFBP-1), insulin, and C-peptide in nondepressed CFS patients and normal controls. We found attenuated basal levels of IGF-I (214 +/- 17 vs. 263.4 +/- 13.4 micrograms/L, p = .036) and IGF-II (420 +/- 19.8 vs. 536 +/- 24.3 micrograms/L, p = .02) in CFS patients and a reduced GH response to hypoglycemia (peak GH; 41.9 +/- 11.5 vs. 106.0 +/- 25.6 mU/L, p = .017). Insulin levels were higher (7.6 +/- 1.0 vs. 4.3 +/- 0.8 mU/L, p = .02) and IGFBP-1 levels were lower (19.7 +/- 4.6 vs. 43.2 +/- 2.7 mg/L, p = .004) in CFS patients compared with controls. This study provides preliminary data abnormalities of the GH-IGF axis in CFS. It is not apparent whether these changes are components of a primary pathological process or are acquired secondary to behavioral aspects of CFS such as reduced physical activity.

Orthotopic liver transplantation reverses the adverse nutritional changes of end-stage liver disease in children.

The changes in growth and body composition after orthotopic liver transplantation (OLT) were studied in 61 children [median age at OLT 3.49 y (range: 0.04-14.5 y), 26 boys and 35 girls] who had survived > or = 1 y post-OLT. Height, weight, midarm circumference (MAC), triceps skinfold thickness (TSF), and subscapular skinfold thickness (SSF) were measured at OLT, 3 and 6 mo later, then annually up to 5 y. SD scores (SDS) were derived from population standards. Results are reported as mean SDS +/- SEM. At OLT the children were short and malnourished (height: -0.98 +/- 0.22; weight -0.82 +/- 0.18; MAC: -1.77 +/- 0.21; TSF: -1.27 +/- 0.17; SSF: -1.49 +/- 0.17). By 3 mo post-OLT, there was a sustained improvement in MAC (-0.73 +/- 0.22), TSF (-0.48 +/- 0.18), and SSF (-0.50 +/- 0.18). Weight SDS (-0.48 +/- 0.20) improved by 6 mo without significant change in height SDS. The three children with Alagille syndrome were smaller (height, weight, and MAC) than children with other diagnoses but did show catch-up growth. Fulminant hepatic failure was not associated with growth failure before or after OLT. Infants (n = 14) were smaller and more malnourished at OLT (smaller skinfold thicknesses and lower weight SDS) than those who received transplants at an older age. By 1 y post-OLT, the only persisting difference was in TSF. Abnormal liver function at 1 y post-OLT (n = 8) and repeated episodes of steroid-treated rejection (n = 13) were associated with worsening height and weight SDS. The use of tacrolimus for graft salvage from rejection (n = 6) was not associated with growth failure. In conclusion, end-stage liver disease has a more adverse effect on MAC, TSF, and SSF than on height and weight, but a marked and rapid improvement occurred post-OLT. Children who were most severely malnourished and growth restricted at the time of OLT showed the greatest catch-up growth after OLT.

Endocrine and cardiac paracrine actions of insulin-like growth factor-I (IGF-I) during thyroid dysfunction in the rat: is IGF-I implicated in the mechanism of heart weight/body weight change during abnormal thyroid function?

Thyroid hormones are essential for the normal growth and development of many tissues. In the rat, hypothyroidism is associated with growth impairment, and hyperthyroidism with the development of a hypercatabolic state and skeletal muscle wasting but, paradoxically, cardiac hypertrophy. The mechanism by which thyroid hormone produces cardiac hypertrophy and myosin isoenzyme changes remains unclear. The role of IGF-I, an anabolic hormone with both paracrine and endocrine actions, in producing cardiac hypertrophy was investigated during this study in hyperthyroid, hypothyroid and control rats. A treated hypothyroid group was also included in order to assess the effect of acute normalization of thyroid function. Body weight was significantly lower in the hyperthyroid (mean +/- S.E.M.; 535.5 +/- 24.9 g, P < 0.05), hypothyroid (245.3 +/- 9.8 g, P < 0.001) and treated hypothyroid (265.3 +/- 9.8 g, P < 0.001) animals when compared with controls (618.5 +/- 28.6 g). Heart weight/body weight ratios were, however, significantly increased in the hyperthyroid (2.74 +/- 0.11 x 10(-3), P < 0.01) and treated hypothyroid (2.87 +/- 0.07 x 10(-3), P < 0.001) animals when compared with controls (2.26 +/- 0.03 x 10(-3). Serum IGF-I concentrations were similar in the control and hyperthyroid rats (0.91 +/- 0.07 vs 0.78 +/- 0.04 U/ml, P = 0.26), but bioactivity was reduced by 70% in hyperthyroid serum, suggesting a circulating inhibitor of IGF. Serum IGF-I levels (0.12 +/- 0.03 U/ml, P < 0.001) and bioactivity (0.12 +/- 0.04 U/ml, P < 0.001) were significantly lower in the hypothyroid group. Liver IGF-I mRNA levels were not statistically different in the control and hyperthyroid animals, but were significantly reduced in the hypothyroid animals (P < 0.05 vs control). Heart IGF-I mRNA levels were similar in the control and hypothyroid rats, but were significantly increased in the hyperthyroid and treated hypothyroid animals (increased by 32% in hyperthyroidism, P < 0.05; increased by 57% in treated hypothyroidism, P < 0.01). Cardiac IGF-I was significantly elevated in hyperthyroidism (0.16 +/- 0.01 U/mg heart tissue, P < 0.01), was low in hypothyroidism (0.08 +/- 0.01 U/mg, P < 0.01) and was normalized in the treated hypothyroid group (0.11 +/- 0.01 U/mg vs control, 0.13 +/- 0.01 U/mg). Low body mass during both hypothyroidism and hyperthyroidism is therefore associated with reduced systemic IGF bioactivity. In hypothyroidism there is a primary defect in the endocrine function of IGF-I, while in hyperthyroidism serum IGF bioactivity is reduced in the presence of normal endocrine production of this anabolic hormone.(ABSTRACT TRUNCATED AT 400 WORDS)

Response of insulin-like growth factor (IGF)-binding protein-1 (IGFBP-1) and IGFBP-3 to IGF-I treatment in severe insulin resistance.

It has been suggested that recombinant human IGF-I (rhIGF-I) is a potential therapeutic agent in diabetes mellitus. It is known to have glucose-lowering effects in normal individuals, in patients with non-insulin-dependent diabetes (NIDDM) and in extreme insulin-resistant states. IGF-binding proteins (IGFBPs) have the potential to affect the biological activity of rhIGF-I. We have studied the effect of infused rhIGF-I on IGFBP-1 and IGFBP-3 in a patient with Mendenhall's syndrome, a rare insulin-resistant state. During an infusion of 20 mg rhIGF-I, glucose concentrations fell from 44.1 +/- 7.2 to 31.5 +/- 7.2 (S.E.M.) mmol/l (P = 0.001), and insulin and C-peptide levels fell from 920 +/- 62 to 542 +/- 45 mU/l (P = 0.008) and 5466 +/- 633 to 3071 +/- 297 pmol/l (P = 0.02) respectively. Significant lowering of phosphate, magnesium and alkaline phosphatase concentrations was also noted. IGF-I levels rose from 48 +/- 10.2 to 410 +/- 50.1 micrograms/l (P = 0.001), and those of IGF-II fell from 279.8 +/- 8.3 to 104.3 +/- 7.9 micrograms/l (P = 0.001). IGFBP-1 concentrations did not significantly change during the infusion but those of IGFBP-3 increased from 1655 +/- 127 to 2197 +/- 334 micrograms/l (P = 0.002), despite a significant fall in GH concentrations from 10.7 +/- 2.6 to 4.1 +/- 1.1 mU/l (P = 0.007), suggesting that IGFBP-3 regulation is also IGF-I-dependent.(ABSTRACT TRUNCATED AT 250 WORDS)

The evolution of changes in immunoreactive serum insulin-like growth factors (IGFs), IGF-binding proteins, circulating growth hormone (GH) and GH-binding protein as a result of short-term dexamethasone treatment.

Inhibition of growth in man and laboratory animals by glucocorticoid treatment is well recognized, yet we have previously shown that glucocorticoids may paradoxically enhance GH secretion and increase serum insulin-like growth factor (IGF) levels. IGFs circulate bound to high-affinity binding proteins (IGFBPs) which modulate their actions, and circulating GH may be associated with two binding proteins (GHBPs) of which the high-affinity GHBP has been characterized and is structurally identical to the extracellular domain of the GH receptor. We have investigated the time-course of changes in GH, IGFs and their binding proteins induced by glucocorticoid treatment in normal male volunteers (n = 12, age range 22-31 years) sampled at 0800 h daily before and during treatment with dexamethasone (2 mg twice daily) for 5 days. In addition, subjects were sampled at 30-min intervals over 7-h periods (0730-1430 h) during the day prior to dexamethasone (day 0), on day 1 following the first dose of dexamethasone and on day 5 following the last dose of dexamethasone. Mean serum IGF-I rose over the initial 72 h and remained elevated at 96 h (297 +/- 11.5 compared with basal levels of 215.5 +/- 9.3 micrograms/l, P < 0.001) whereas IGF-II levels did not change (472.6 +/- 20.5 vs 450.3 +/- 21.7 micrograms/l, P = 0.97). There was a concomitant rise in serum IGFBP-3 from basal levels of 3.69 +/- 0.23 mg/l to a peak at 5 days of 4.16 +/- 0.21 (P = 0.003 vs day 1).(ABSTRACT TRUNCATED AT 250 WORDS)

Differential effects of malnutrition, bile duct ligation and galactosamine injection in young rats on serum levels and gene expression of IGF-binding proteins.

Hepatic gene expression and circulating levels of IGF-binding proteins (IGFBP)-1 to -4 were examined in two rat models of liver disease employing acute hepatitis or chronic structural damage. The study comprised four groups: group 1 (n = 6) was injected intraperitoneally with saline and food was available ad libitum (AL), group 2 (n = 6) underwent bile duct ligation (BDL), group 3 (n = 6) was injected with 400 mg galactosamine (GAL), group 4 (n = 6) was sham-operated and pair-fed to group 2 (PF). All were killed by decapitation at day 7. Serum IGF-I, by RIA, was significantly (P < 0.05) lower in the BDL group (458 +/- 37 micrograms/l) and PF group (451 +/- 51 micrograms/l) compared with the AL group (643 +/- 77 micrograms/l) and GAL group (720 +/- 67 micrograms/l). Immunoblotting showed raised IGFBP-2 levels in all groups compared with AL (BDL, 167 +/- 14% of AL; GAL, 173 +/- 13%; PF, 149 +/- 9%). IGFBP-3 was decreased in the GAL (56 +/- 11%) and PF groups (66 +/- 5%) but increased in the BDL group (154 +/- 29%). IGFBP-4 was decreased in the GAL (76 +/- 11%) and PF groups (47 +/- 5%) but unchanged in the BDL group (90 +/- 10%). By Northern analysis, IGFBP-1 mRNA expression was increased in the GAL (321 +/- 51%) and PF groups (263 +/- 12%) but reduced in the BDL group (68 +/- 8%). IGFBP-2 expression increased in all groups (PF, 836 +/- 19%; BDL, 683 +/- 121%; GAL, 372 +/- 68%) and was highest in the BDL and PF groups. IGFBP-3 expression was reduced in all groups (BDL, 57 +/- 16%; GAL, 52 +/- 12% PF, 51 +/- 13%). IGFBP-4 expression was reduced in the GAL (30 +/- 4%) and PF (28 +/- 5%) groups but unchanged in the BDL group (76 +/- 9%). Marked changes in gene expression of IGFBPs occurred in both models of liver disease, together with serum changes, which were different from each other and from malnutrition alone.