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Biomedical subjects

Z Hochberg

Publications and source records attributed to Z Hochberg.

At least 73 records · Page 4Linked to original sources
PubMed1993

The turnover of growth hormone (GH)-binding protein and GH receptor in rabbit and rat.

The present study was undertaken to further explore the comparative dynamics of growth hormone-binding protein (GH-BP) in relation to the turnover of the GH-receptor (GH-R) in vivo in rabbits and rats. The strategy used was to examine the time course of hepatic GH-R turnover over a 3 h period after cycloheximide treatment, with simultaneous measurements of serum GH-BP level. In the rabbit we sampled multiple liver biopsies and serum samples consecutively from each animal. In the rat, experiments on individual animals were conducted for each time point. In the rat, both liver GH-R and serum GH-BP declined after cycloheximide injection following first-order kinetics. The t 1/2 values for GH-R and GH-BP were 29.7-44.5 and 82.7-119.5 min (95% confidence limits), respectively. A significant positive correlation was found between rat liver GH-R and serum GH-BP (r = 0.85; p < 0.001). In contrast, the decline in rabbit liver GH-R, following cycloheximide treatment was accompanied by simultaneous time-dependent accumulation of serum GH-BP. The t 1/2 for rabbit serum GH-BP accumulation was 30.4-67.6 min. Scatchard analysis of [125I]hGH binding to rabbit GH-BP indicated that the binding capacity increased from 2818 +/- 538 fmol/ml, at time zero, to 5236 +/- 419 fmol/ml following 60 min cycloheximide treatment (p < 0.05). No significant changes in affinity were observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Effect of growth hormone on gastrocnemius muscle of aged rats after immobilization: biochemistry and morphology.

Immobilization of limbs of aged animals is associated with swift muscular damage and atrophy. We investigated the effect of rat growth hormone (rGH) on immobilized hindlimb muscles of 26-mo-old rats. Administration of rGH significantly reduced muscle weight loss and muscle protein oxidation caused by immobilization. Capillary blood volume, measured by photoplethysmography of the hindlimb, showed a 34% reduction in immobilized animals, which was eliminated by rGH. The activity of creatine phosphokinase in immobilized gastrocnemius muscle was significantly reduced by immobilization. This damage was diminished by rGH administration. Similarly, the increase in acid phosphatase activity in immobilized muscle was reduced after rGH treatment. Morphologically, marked muscle atrophy and fiber disorientation were observed in immobilized limbs. Therapy with rGH prevented some of these changes. These results indicate that administration of rGH may provide a useful means to attenuate the degenerative effects of limb immobilization of aged rats, as evident from physiological, biochemical, and morphological parameters.

Acid Phosphatase↗
PubMed1993

Ontogenesis of the sexual dimorphism of growth hormone secretion by perifused rat hemipituitaries.

The aims of the present study were to investigate the sexual dimorphism and the role of sex steroids in GH secretion at the pituitary level, and to evaluate the ontogenesis of these effects. Towards these aims we used an in vitro perifusion system of hemipituitaries under a simulated milieu of hypothalamic factors: two 3-min pulses of GHRH at 3-hour intervals were separated by continuous flow of somatostatin. Rat GH was measured in 2.4-min fractions and analyzed by the pulse analysis program PULSAR. Pulses were similar in prepubertal male and female rats, but sexual dimorphism was evident in adults. In adult males, who had undergone neonatal gonadectomy, GH pulse amplitude and area under the curve (AUC) were lower compared to control. When gonadectomy had been performed at a prepubertal age, the pulse amplitude was still lower, but the AUC was not different from control. The gap between orchiectomy at neonatal and prepubertal age indicates the perinatal imprint, which induces an increase in AUC. Neonatal testosterone treatment of intact female rats had no effect on GH secretion by adult pituitaries. In neonatally gonadectomized female rats, under neonatal testosterone treatment, the pulse amplitude increased. A similar increase was observed after neonatal gonadectomy without testosterone treatment. We conclude that the sexual dimorphism of GH secretion is partially induced at the pituitary level and its response to the hypothalamic hormones. We assume that a neonatal imprint effect of testosterone in the male induces primarily an increase in AUC in response to GHRH. The imprint in females influences the GH pulse amplitude and AUC.

Aging↗
PubMed1993

Growth hormone-binding protein in partially hepatectomized rats.

The role of the liver in regulating serum growth hormone-binding protein (GH-BP) was studied. We measured rat serum GH-BP and insulin-like growth factor 1 (IGF-1) 30 min to 96 h after 70% partial hepatectomy (PHP) or sham operation in adult male rats. Serum GH-BP declined sharply from 5.8 +/- 0.1% at baseline to 3.9 +/- 0.5% by 48 h following PHP. By 72 h serum GH-BP at baseline to 3.9 +/- 0.5% by 48 h following PHP. By 72 h serum GH-BP returned to baseline level and remained at that level 96 h postoperatively. In sham-operated female rats, serum GH-BP was about 2-fold higher than in males (10.5 +/- 1.46 versus 5.8 +/- 0.2%), whereas 24 h after hepatectomy a significant drop of about 50% was observed (p < 0.001). Serum IGF-1 decreased within 2-4 h postoperatively in both sham-operated and PHP groups, but thereafter was lower in the PHP rats, up to 48 h after operation, compared to sham-operated rats (p < 0.03). The study shows that the liver has an important role in the determination of serum GH-BP levels. The return to normal GH-BP level, even before the liver regained its full size following hepatectomy, suggests an increase in GH-BP production by the regenerating liver.

Animals↗
PubMed1993

Insulin-like growth factor I accelerates proliferation and differentiation of cartilage progenitor cells in cultures of neonatal mandibular condyles.

The present study examined the effect of exogenous IGF-I on growth and development of neonatal cartilage of the mandible condyle. Condylar cartilage was cultured as organ culture. The explants were cultured on top of collagen sponges in medium containing 2% fetal calf serum and were treated with IGF-I at doses ranging from 3.25 to 26 nmol/l for up to six days. IGF-I was found to increase significantly the uptake of [3H]-thymidine and [35S]-sulfate in a dose-related manner. The enhanced cellular proliferation, along with the increased synthesis of proteoglycans, resulted in a substantially larger mass of tissue in the organ culture system. The nature of the IGF-I stimulative effect was further studied through the use of a tissue culture system whereby a separated chondroprogenitor zone is cultured under conditions which favor its development at first into cartilage and then into bone. Using this culture system, we could show that IGF-I induces merely the de novo chondrogenesis process. This was reflected in the appearance of relatively large amounts of cartilage specific antigens such as type II collagen, cartilage proteoglycans, chondrocalcin and 100 KDa protein. Yet, no bone specific antigens were significantly increased, as is the case with GH effects. These results indicate that IGF-I is a strong chondrogenetic agent. But, unlike growth hormone, it does not seem to stimulate bone formation.

Analysis of Variance↗
PubMed1992

Interactions between growth hormone and dexamethasone in skeletal growth and bone structure of the young mouse.

The present study investigated the interactions of growth hormone (GH) and glucocorticoid on skeletal growth and bone structure in young mice. The purpose of this study was to examine the possible prevention by GH of the damage inflicted by dexamethasone (Dex) at sites of skeletal growth and ossification. Dex (1 mg/kg) with or without rat GH (rGH) or bovine GH (bGH), 1 mg/kg, was given for 4 weeks, from age 3-7 weeks, to female ICR mice. Tibiae, humerus, and vertebrae were analyzed morphometrically and biochemically. Growth, as determined by the mouse weight, tibial length, and humerus protein content was found to be compromised by dexamethasone. This was prevented by rGH or bGH. The epiphyseal growth plate width, trabecular bone volume, cortical bone width, mineral bone content, and alkaline and acid phosphatase activity were decreased by dexamethasone. These were prevented by rGH or by bGH. The findings of the present study suggest that in the mouse, GH can decrease or even avoid some of the pathological features in growing bones inflicted by high-dose glucocorticoid treatment.

Analysis of Variance↗
PubMed1992

The distal axis of growth hormone (GH) in nutritional disorders: GH-binding protein, insulin-like growth factor-I (IGF-I), and IGF-I receptors in obesity and anorexia nervosa.

The endocrine abnormalities along the growth hormone (GH) axis in anorexia nervosa (AN) and in obesity include hypothalamic, pituitary, and peripheral elements. The present study was undertaken to evaluate the effects of these nutritional extremes on GH-binding protein (BP) levels and on Insulin-like growth factor-I (IGF-I) receptors on red blood cells (RBC). Nine patients with AN and 20 obese subjects were compared with normal control children, adolescents, and adults. GH-BP was measured by a binding assay with dextran-coated charcoal separation. IGF-I binding was measured on enriched RBC. Serum GH-BP levels were markedly reduced in the AN patients, and highly increased in the obese. Scatchard analyses showed linear plots with unaltered binding affinities (Ka). The binding capacity (Bmax) was significantly lower than normal control in the AN patients and higher in the obese. GH-BP levels correlated positively with the body mass index (BMI). RBC [125I]IGF-I binding was significantly elevated in the AN patients and low in the obese. Scatchard analyses showed curvilinear plots. The high-affinity constants (Ka1) were slightly, but significantly, higher in the AN patients and in the obese compared with control. The binding capacity of the first binder (Bmax1) was lower in obesity than in AN or control. The low-affinity constants (Ka2) were similar in the three groups, and its binding capacity (Bmax2) was similar in the AN patients and the controls, but significantly lower in the obese. [125I]IGF-I binding correlated negatively and significantly with the BMI and with the GH-BP.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

Effect of human growth hormone (GH)-binding protein in human serum on GH binding to rabbit liver membranes.

The sequence identity of growth hormone-binding protein (GH-BP) with the extracellular domain of GH receptors raised the possibility that circulating GH-BP might affect the binding of human GH (hGH) to its receptors, and thus, its biological effects. To test this hypothesis, we tested the effects of sera with low GH-BP levels (obtained from prepubertal children, girls with anorexia nervosa [AN], and patients with hepatic cirrhosis), normal control sera, and sera with high GH-BP levels (obtained from obese patients) on hGH binding to its receptors. GH-BP activity in patients' sera was measured by incubation with [125I]hGH and the separation of bound hGH from free hGH with dextran-coated charcoal. The effect of GH-BP was studied by preincubation of patients' sera with increasing concentrations of hGH, followed by incubation with [125I]hGH and a rabbit liver membrane preparation known to be rich in GH receptors, and finally by measuring hGH bound to the receptors. In this study, we report on the ability of GH-BP to reduce the inhibitory capacity (IC50) of hGH on [125I]hGH binding to GH receptors. The concentration of GH-BP in serum is positively correlated with the IC50 of hGH incubated with different sera on [125I]hGH binding to its receptors (n = 21; r = .886, P less than .001). In the presence of high serum GH-BP levels, such as those observed in obesity (20.13% +/- 0.71%/0.05 mL serum), the IC50 values were significantly higher than those obtained with sera containing GH-BP levels lower than those measured in human control subjects, such as from prepubertal children, AN patients, and cirrhotic patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Modulation of human growth hormone binding to somatogenic and lactogenic receptors by monoclonal antibodies to human growth hormone.

The relationship between the structure of human growth hormone (hGH) and the hormone-receptor interaction was investigated by studying the effects of specific monoclonal antibodies (MAbs) to hGH on the binding of [125I]hGH to rabbit liver and mouse liver microsomes. Receptor binding assays were carried out using a constant dose (1 ng) of [125I]hGH and varying concentrations of MAbs. The assay was carried out in the presence of either excess ovine prolactin for the measurement of somatogenic (SOM) binding sites, or excess bovine growth hormone for the determination of lactogenic (LAC) binding sites. Anti-hGH MAbs were found to have a whole spectrum of effects on hGH binding, including inhibitory, non-effect and enhancing activities. Enhancement of the binding of [125I]hGH to both SOM and LAC receptors was observed in liver membranes of rabbit or mouse. The observed amplified signal of [125I]hGH binding to various receptors in the presence of MAb no. 8 may be due to conformational changes which occur following MAb binding to hGH. On the other hand, most of the other MAbs caused inhibition of [125I]hGH binding. A negative correlation exists between the cross-reaction of various MAbs with the N-terminus truncated forms of hGH (Met14-hGH or Met8Leu-hGH) and their respective KD/IC50 values enabled the evaluation of the crucial role of the N-terminus region in hGH binding to both LAC and SOM receptors. MAb nos 1 and 19, which are directed towards acid residues 95-134 and the C-terminus, inhibited SOM binding more potently than LAC binding. Thus, it seems that these mid-molecule and C-terminus regions are also important in hGH binding, and that they play a role in the partial overlap of SOM and LAC binding.

Animals↗
PubMed1992

Calcium therapy for calcitriol-resistant rickets.

Ten patients with calcitriol-resistant rickets caused by a defect in the ligand-binding domain of the vitamin D receptor are described. Eight patients, 1.7 to 13.8 years of age, received high doses of elemental calcium (range, 0.4 to 1.4 gm/m2) through indwelling intracaval catheters for periods of 1.8 to 3.8 years. Two other patients, aged 1.1 and 2.2 years, were given oral calcium therapy as the sole mode of treatment. In five of the intravenously treated patients, oral calcium therapy was initiated after radiologic evidence of healing of the rickets. To maintain normal serum calcium concentration, the patients required daily doses of elemental calcium of 3.5 to 9 gm/m2 body surface area. Clinical improvement was observed within a week of the start of intravenous therapy, with disappearance of bone pain; several of the younger patients started to walk for the first time. Growth velocity increased within 2 to 3 months, from a pretreatment rate of -0.8 to -6.3 standard deviation score (SDS), to a posttreatment rate of +0.1 to +5.1 (SDS). Serum calcium, parathyroid hormone, phosphorus, and alkaline phosphatase values returned to normal within a year. Radiologic signs of healing occurred more rapidly in the intravenous treatment groups and in younger patients. Episodes of septicemia occurred frequently in those receiving parenteral therapy and required replacement of the catheter. We recommend that in the treatment of calcitriol-resistant rickets, oral calcium therapy be started at the youngest possible age, in doses to the limit of intestinal tolerance. When rickets is present, calcium should be infused through a large vessel in doses high enough to produce normocalcemia, normophosphatemia, and suppression of parathyroid hormone. Only after radiologic healing has been observed can oral calcium therapy be introduced.

Administration, Oral↗
PubMed1992

Growth-hormone-binding protein in patients with acromegaly.

The present study was undertaken to investigate the possible regulatory effect of chronic exposure to human growth hormone (hGH), in patients with acromegaly, on growth-hormone-binding protein (GH-BP). Nineteen patients with active acromegaly, before, during or after treatment, comprised the subjects of this study. Serum GH was measured by radioimmunoassay and GH-BP by a binding assay with dextran-coated charcoal separation. The specific binding of [125I]hGH (1 ng) obtained with 50 microliters serum was expressed as a percentage of total cpm. To evaluate the impact of the lower GH-BP on GH activity, we studied the effect of acromegalic serum on hGH displacement of [125I]hGH binding to GH receptors in rabbit liver membranes. Compared to normal controls (11.43 +/- 0.37%), the acromegalic patients had low serum levels of GH-BP (5.45 +/- 0.40%; p < 0.001), which correlated negatively with serum GH levels (p < 0.01). In 7 patients, GH-BP normalized within 2-3 months of successful therapy. The lower GH-BP was due to a reduction in binding capacity, whereas binding affinity remained unchanged. Acromegalic serum, with its low GH-BP, resulted in a shift to the left of the GH displacement curve when compared with normal human sera: IC50 values were 7.47 +/- 0.29 and 11.19 +/- 0.84 ng (p < 0.02) for acromegalic and normal human sera, respectively. We conclude that acromegaly is characterized by low levels of GH-BP due to a decrease in serum-binding capacity. The decrease in GH-BP may render the acromegalic serum GH relatively more active in the GH receptor assay.

Acromegaly↗
PubMed1992

Roles of pulsatility and continuity of growth hormone (GH) administration in the regulation of hepatic GH-receptors, and circulating GH-binding protein and insulin-like growth factor-I.

GH secretion in the male rat is characterized by regular GH peaks of high amplitude, and their GH receptors and GH-binding protein (BP) are low. Female rats have a more continuous secretion, and their GH receptors and GH-BP are high. To determine how the pattern of GH delivery may affects the physiological responses to the hormone, hypophysectomized male rats were infused with human GH (1.5 U/kg.day) for 5 days through an implanted iv cannula in either a pulsatile manner (for 5 min every 3 h) or continuously. We then measured free and total (after MgCl2 treatment) somatogenic and lactogenic receptors in hepatic cell membranes, and GH-BP and immunoreactive insulin-like growth factor-I (IGF-I) in serum. The concentrations of occupied, but not free, somatogenic and lactogenic binding sites were higher 5 min after a 5-min infusion of human GH than 90 min after the infusion. Consequently, the total levels (free plus ligand binding) of somatogenic and lactogenic receptors were also higher 5 min after a GH pulse than after 90 min. The levels of circulating GH-BP were higher 90 min than 5 min after a GH pulse, and the serum IGF-I levels did not differ between these time points. The concentrations of free and total somatogenic and free lactogenic receptors in the liver, as well as GH-BP and IGF-I in circulation were higher and body weight gain was lower in rats given continuous GH infusion than after pulsatile infusions. It is concluded that the nature of GH-levels profile has a marked influence on the interrelationship of GH, GH receptors, GH-BP, serum IGF-I and growth, whereby the later is stimulated maximally by pulsatile GH-levels, while the receptor and GH-BP are enhanced maximally by continuous levels. The basis for this discrepancy may lay in the competitive power of GH-BP toward GH receptor binding. A pulsatile GH pattern induced cyclicity in the levels of hepatic cell membrane GH receptors and circulating GH-BP. It is suggested that these factors are regulated in a similar way by the plasma GH pattern in pituitary intact rats.

Animals↗
PubMed1992

Growth hormone and insulin-like growth factor-I increase macrophage uptake and degradation of low density lipoprotein.

Hyperlipidemia has been reported in adults with hypopituitarism, and human (h) GH therapy has been shown to lower plasma cholesterol in patients with hypercholesterolemia. Macrophage cholesterol accumulation is an early event in atherosclerosis, and these cells have been shown to respond to GH and insulin-like growth factor (IGF-I). The present study was aimed at investigating the activity of GH and IGF-I in macrophages, and used murine macrophages as a model system to investigate the effects of GH and IGF-I on cellular uptake and metabolism of low density lipoprotein (LDL). The J-774 murine macrophage cell line was shown to bind hGH, to respond to hGH by an increase in cell IGF-I content, and to have specific high affinity binding sites for IGF-I. Mouse peritoneal macrophages and the J-774 macrophage cell line respond to hGH with a dose-dependent stimulation of cellular association and degradation of LDL as well as an enhanced cholesterol esterification rate. A similar response was observed after in vitro treatment of the cells with IGF-I. Preliminary results in human monocyte-derived macrophages showed similar results. The dependency of the effect of hGH on locally produced IGF-I was shown by abrogation of the hGH effect after adding anti-IGF-I antibody to the culture medium. It is concluded that murine macrophages possess the machinery to bind GH, produce IGF-I, and bind IGF-I. This machinery is used by macrophages, and apparently by other cells, to execute GH-dependent IGF-I-mediated stimulation of cellular uptake and metabolism of LDL. This may provide the explanation for both the elevated plasma LDL concentration in patients with GH deficiency and the effect of GH therapy to reduce plasma LDL levels.

Animals↗
PubMed1992

Growth hormone- and prolactin-binding proteins in mammalian serum.

The present study was undertaken to characterize the species specificity and diversity of lactogenic and somatogenic binding to serum among mammals and to classify GH-binding protein (GH-BP) in this group of species. Animal sera were characterized on the basis of human (h) GH and bovine (b) PRL binding levels, binding specificity toward GHs and PRLs, binding affinity constant (Ka), and the ability of a monoclonal antirabbit GH receptor antibody (MAb-7) to inhibit the binding to serum. Analyses of the results yielded a classification of the mammalian sera into five types of GH binding, which we elected to call GH-BP. The guinea pig had undetectable levels of GH-BP and was labeled type 0. Type I GH-BP was found in the mouse and the rat. hGH binding to GH-BP of type I serum was of low affinity (1.2-3.9 x 10(8) M-1) with high IC50 (approximately 100 ng/tube) and was purely somatogenic in nature. Type II GH-BP was found in the goat, sheep, and cow. Their IC50 of hGH binding was approximately 4-fold lower than that of type I GH-BP. Their binding of hGH was relatively specific and only marginally displaced by the PRLs. Type III GH-BP was found in the rabbit, horse, cat, dog, and pig. These animals' sera had high affinity binding toward hGH (4.7-9.2 x 10(9) M-1), with low IC50 (approximately 2 ng/tube) and dominant lactogenic binding. The great similarity of type III GH-BPs was further stressed by the ability of MAb-7 to inhibit [125I]hGH binding to all type III sera, but not to the other mammalian sera tested. Type IV GH-BP was found in the human and rhesus monkey sera. These were characterized by binding affinities that were intermediate between those for types II and III GH-BP and by the inability of nonprimate GHs to compete with hGH binding. To directly confirm the potent effect of the lactogenic hormones in type III GH-BP, the specific binding of bPRL to sera of type III animals was studied. [125I]bPRL-specific binding was determined under optimized assay conditions and was the highest in rabbit serum, with the following rank order being observed: rabbit >> horse = dog = pig > cat. Scatchard analysis of [125I]bPRL binding revealed linear plots with similar affinity constants (Ka) of 1.7-3.3 x 10(9) M-1.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1991

[Growth hormone for Turner's syndrome].

Short stature is a prominent feature of Turner's syndrome. Various anabolic steroids and estrogens have been used, but the recent availability of biosynthetic human growth hormone (hGH) has led to its clinical evaluation in this syndrome. 10 girls with the syndrome, aged 5-13.8 years (mean 10.8), were treated with recombinant hGH. Height after 12 months of treatment was significantly greater than before treatment. The accelerated growth velocity after 1 year of treatment continued for longer periods. Girls who completed 3 years of treatment have exceeded their untreated expected adult height. No adverse reactions were noted and compliance was good. These results indicate that hGH is useful for accelerating growth velocity in patients with Turner's syndrome. Therapy that normalizes height during childhood may have important psychologic effects, and is likely to influence the child's self-image and peer relationships.

Adolescent↗
PubMed1991

The growth hormone binding protein as a paradigm of the erythropoietin superfamily of receptors.

The growth hormone (GH) receptor belongs to a novel receptor family which shares significant amino-acid sequence homology and includes prolactin receptors, erythropoietin receptors and several cytokines' receptors. GH and three other members of this family of receptors have been shown to have circulating soluble forms. The present review summarizes our knowledge on receptor related binding proteins, discusses their possible biological effects and suggests their use in novel assays for their ligands. The GH-binding protein (GH-BP) was the first to have been described and is used as a model for the concept. A series of indirect pieces of evidence suggest that the measurement of circulating GH-BP may enable an evaluation of the GH-receptor. When covalently bound to GH, GH-BP has been shown to slow the clearance of GH. On the other hand GH-BP competes with the GH-receptor for GH binding and, thus, diminishes the biological effect of GH. We suggest a biological role for GH-BP as follows: an increase in the availability of GH results not only in the upregulation of the GH-receptor but also in increased turnover of this receptor, its internalization and recycling. This is followed by a concomitant increase in GH-BP which, in turn, mitigates the effect of GH by competing with the receptor on GH binding. The extracellular domain of the GH-receptor is homologous, to a large extent, with the sequence of several receptors for hormones and cytokines, which have recently been cloned.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Effects of hypo or hyper-thyroidism on growth hormone-binding protein.

OBJECTIVE: Growth hormone (GH) receptors are influenced by the thyroidal state of experimental animals. It has been suggested that GH-binding protein (BP) might serve as an indirect measure of the GH receptors. The present study was undertaken to investigate the growth hormone binding protein in patients with hypo or hyperthyroidism. PATIENTS: Patients included 42 adults with untreated hyperthyroidism (FT4 greater than 25 pmol/l; TSH less than 0.15 mU/l) and 29 adults and three children with untreated hypothyroidism (FT4 less than 10 pmol/l; TSH greater than 15 mU/l). MEASUREMENTS: Growth hormone binding protein was measured by a binding assay with dextran-coated charcoal separation. The specific binding of 125I-human GH (1 ng) obtained with 50 microliters serum was expressed as a percentage of the total c.p.m. RESULTS: Growth hormone binding protein specific binding in hypothyroid adults and children was significantly lower than in their respective controls in both adults and children (P less than 0.001). In patients with FT4 levels greater than 40 pmol/l, the mean (+/- SEM) growth hormone specific binding (12.89 +/- 0.59%) was higher than in controls (P less than 0.05). However, in 15 hyperthyroid patients with levels of FT4 of 25-40 pmol/l, the mean growth hormone binding protein specific binding (11.22 +/- 0.76%) was not different from that in normal human subjects. The affinity constants (Ka) obtained by Scatchard analysis for the hypothyroid and hyperthyroid patients' sera were not significantly different from that for normal human sera. Binding capacity for the hypothyroid sera was significantly lower (P less than 0.02), while that of hyperthyroid sera was increased (P less than 0.001). CONCLUSIONS: Growth hormone binding protein correlates positively with the thyroid status. It can be indirectly deduced that this reflects a similar relationship with the human GH receptor.

Adult↗