Induction of growth hormone release by Pueraria thunbergiana BENTH.

Puerariae Radix (PR), Puerariae Flos (PF), and Puerariae Surculus (PS) as well as their constituents were tested for induction of rat growth hormone (rGH) release by both rat pituitary cell culture and in vivo experimentation in order to develop them to novel drugs. Through a calibration curve of the rGH released by addition of rat growth hormone-releasing hormone (rGHRH) to rat pituitary cells, the 70 % ethanol extracts of PR and PS increased rGH release by about 1.6 and 1.7 times as high, respectively, as the control group (264.6 +/- 13.6 pM). However, each puerarin type as a representative constituent of PR in Korea Pharmacopeia (KP) and tectorigenin and an important ingredient of PF were twice as effective as in the control group. The acid hydrolysate of Puerariae Surculus (HPS) increased rGH release concentration-dependently, and its EC (50) was approximately 10.4 microg/ml. The T (max) value for rGH after injection of 20 microg/kg of rGHRH was 10 - 30 min, while the C (max) value was increased by approximately 12-fold compared to the control group (198.2 +/- 25.0 pM) and the AUC (0 - 45) was increased to 10 times the level of the control group (10,840.9 +/- 845.5 min. pM). On the other hand, T (max) for the HPS was 60 min, while C (max) was increased approximately to 5.8 fold compared to control (244.1 +/- 36.4 pM). C (max) for puerarin was 1,028.6 +/- 502.7 pM, that is, approximately 5.2 times as high as the control level. However, tectorigenin (20 microg/kg) was of no statistical significance. Therefore, we suggest that the HPS and puerarin act either on GH secretagogue receptors or on GHRH receptor of somatotrophin as possible agonists or an inhibitor on somatostatin receptor to release rGH, respectively.     

Induction of growth hormone release by dioscin from Dioscorea batatas DECNE

In this study, dioscin was isolated from Dioscoreae Rhizoma (DR), which is the rhizome of Dioscorea batatas D(ECNE). that inhabits broad areas of Korea and Japan. To determine whether dioscin induced growth hormone (GH) release, we evaluated its induction effects on GH release both in vitro and in vivo. The 70% methanol extract of DR, and its n-hexane and n-BuOH fractions, induced rat GH (rGH) release in rat pituitary cells 10-fold, 8-fold, and 5- fold higher than the control (0.36 +/- 0.02 nM), respectively (p < 0.05 each). The dioscin-induced rGH release of the cells was concentration-dependent and its ED(50) was 1.14 x 10(-5) M. Within 90 minutes after intravenous administration of 10 microg/kg (p < 0.05 at t(max)), dioscin caused the greatest increase in rGH concentration (C(max)) in the rat plasma (34.16 +/- 14.10 ng/ml) (n = 4), which was twice as high as the control group (12.88 +/- 3.29 ng/ml) (n = 27).     

Effects of varying the position of thyroid hormone response elements within the rat growth hormone promoter: implications for positive and negative regulation by 3,5,3'-triiodothyronine

The thyroid hormone response element (T3RE) of the rat GH (rGH) promoter is located at -188 to -165 relative to the mRNA start site (TSS). Similar sites have been identified in other genes regulated by T3. We have investigated some of these T3REs in positions within the rGH promoter to assess the relative influences of DNA-binding site and position on positive and negative regulation by T3. Synthetic oligonucleotides were used with sequences from the rGH T3RE and proposed negative T3REs (nT3RE) from the rat and human alpha-subunit and rat beta TSH genes. The nT3REs were placed in the background of the wild-type rGH promoter in two positions, at -55 and down-stream of the TSS, with up- and down-mutations of the rGH T3RE. Rat GH T3RE elements were placed 700 basepairs up-stream of a basal rGH promoter and some also at the -55 and TSS positions. Constructions were tested in a transient transfection assay in rat pituitary tumor cells. Two copies of the rGHPAL (palindromic T3RE) placed 700 basepairs up-stream of the rGH promoter conferred 10-fold T3 induction. In the -55 position, the rGHPAL increased T3 induction compared to that in controls, whereas a fragment from the rat and human alpha-subunit gene in the same position reduced induction. Negative T3REs from rat beta TSH and human alpha-subunit reduced T3 induction 50% when placed at the TSS position of a rGH promoter containing an up-mutant T3RE. The T3REPAL placed at the same site increased T3 induction.(ABSTRACT TRUNCATED AT 250 WORDS)     

Actions of L-363,586, a cyclic hexapeptide analogue of somatostatin, on GH secretion by human somatotrophinoma cells in vitro.

L-363,586 is a cyclic, hexapeptide analogue of somatostatin-14 with potent inhibitory actions on rat growth hormone (GH) release in vitro. The studies reported here investigate the direct effects of L-363,586 on basal and growth hormone-releasing factor (GRF)-stimulated GH secretion from 3 human somatotrophinomas in dispersed cell culture. 1nM and 10nM L-363,586 inhibited both basal and GRF-stimulated GH release from cells of all 3 somatotrophinomas during a 2h treatment period, whilst 100nM L-363,586 had a prolonged inhibitory action on basal GH secretion from cells of 2 of the tumours throughout treatment and recovery periods. Rebound release of GH was observed with cells of 1 tumour following treatment with L-363,586 plus GRF. The actions of L-363,586 were similar to those of somatostatin-14. These data suggest that L-363,586 may have a role in the treatment of acromegaly.     

Effect of acute intravenous administration of delta-9-tetrahydrocannabinol on the episodic secretion of immunoassayable growth hormone in the rat.

Blood samples from unrestrained, unanesthetized, male rats (300-350 g) were obtained every 15 min. for 9 consecutive hrs. (1000-1900 h). Each rat received, intravenously, a vehicle injection (controls) or a 2.0 mg/kg dose of delta-9-tetrahydrocannabinol (THC) at 1300 h to determine the effect of this drug on the spontaneous episodic secretion of plasma immunoassayable rat growth hormone (rGH). Acute administration of THC suppressed the secretion of rGH, as is evident from mean plasma level (p less than .01), peak height (p less than .02), and integrated peak amplitude (p less than .02) analyses. Episodic secretion was inhibited in all animals (n = 7) receiving THC. Although further investigation is needed to define clearly the physiological mechanisms involved in this response, these data indicate that THC can inhibit the hypothalamic-pituitary control of normal episodic growth hormone secretion in the rat.     

Variations in prolactin and growth hormone production during cellular growth in clonal strains of rat pituitary cells.

A permanent, clonal strain of rat pituitary tumor cells (GH3-cells) spontaneously synthesizes and secretes prolactin (rPRL) and growth hormone (rGH) into the culture medium. The rates of hormone production (microng extracellular hormone/mg cell protein/24 hours) and synthesis (vida infra) as well as the rate of [3H]thymidine incorporation into DNA (DNA synthesis) have been studied. During logarithmic growth rPRL and rGH production increased to 160 and 250% of the value at day 2 after plating, while during the plateau phase of cell growth hormone production decreased to initial values. The fluctuations in rPRL production could be fully explained by variations in the rate of rPRL synthesis: [3H]eucine incorporated into rPRL as measured with immunoprecipitation and polyacryl-amide gel electrophoresis. Also the rates of synthesis and production of rGH showed parallel changes during exponential and plateau phase of growth, but this hormone was probably degraded intracellularly. The relative reduction in the rate of synthesis of rPRL and rGH during the plateau of growth corresponded closely to the fall in the rate of DNA synthesis. The reduction in rPRL synthesis could not be explained through an inhibition by extra-cellular rPRL accumulation or by cell to cell interaction occurring in dense cultures. The intracellular concentrations of both hormones were unaltered during logarithmic growth, but rose to 500% for rPRL and 200% for rGH during the plateau phase. In spite of the marked variations in basal rPRL and rGH production the GH3 cultures of different ages were equally able to increase rPRL and decrease rGH production in response to thyrotropin releasing hormone (3 X 10(-7) M) and 17beta-estradiol (10(-8)M).     

Functional characterization of the rat growth hormone promoter elements required for induction by thyroid hormone with and without a co-transfected beta type thyroid hormone receptor

We have extensively characterized the sequences of the rat growth hormone (rGH) promoter required for induction by T3 (thyroid hormone, 3,5,3'-L-triiodothyronine) in a transient transfection system. Oligonucleotides containing portions of the rGH promoter sequence with various deletions and point mutations were placed upstream of the first 137 base pairs of the rGH promoter or the heterologous herpes virus thymidine kinase promoter in chloramphenicol acetyltransferase expression vectors. The rGH137 and thymidine kinase promoters show no or minimal response to T3 in the basal state. The constructs were tested in GH4C1 rat pituitary cells and COS cells (functionally deficient in thyroid hormone receptor) with and without a co-transfected plasmid expressing a beta type c-erbA gene coding for a functional T3 receptor. Oligonucleotides containing the T3 receptor binding site confer hormone-dependent induction in a manner that is independent of either orientation or variation in position on the helix relative to the promoter. Point mutations in the sequence -189 to -173 result in loss of T3 induction, and bases between -173 and -167 were also required for a full T3 response. The minimal length to confer T3 induction to the rGH promoter was 23 base pairs (-190 to -167). Point mutations creating a perfect duplication of 7 base pairs within the receptor binding site conferred 12-fold T3 response to the rGH137 promoter, 3-fold greater than the wild type rGH237 construct. T3 inductibility was also transferred to the thymidine kinase promoter by an oligonucleotide containing the sequence -200 to -157, demonstrating that cell type specific elements located 3' to 157 of the rGH promoter are not required for thyroid hormone responsiveness.     

The differential effects of galanin-(1-30) and -(3-30) on anterior pituitary hormone secretion in vivo in humans

Intravenous injection of galanin increases plasma growth hormone (GH) and prolactin (PRL) concentrations. In the rat, the effects of galanin on GH appear to be mediated via the hypothalamic galanin receptor GAL-R(1), at which galanin-(3-29) is inactive. In contrast, the effect of galanin on PRL is mediated via the pituitary-specific galanin receptor GAL-R(W), at which galanin-(3-29) is fully active. We investigated the effects of an intravenous infusion of human galanin (hGAL)-(1-30) and -(3-30) on anterior pituitary hormone levels in healthy females. Subjects were infused with saline, hGAL-(1-30) (80 pmol. kg(-1). min(-1)), and hGAL-(3-30) (600 pmol. kg(-1). min(-1)) and with boluses of gonadotropin-releasing hormone, thyrotropin-releasing hormone, and growth hormone-releasing hormone (GHRH). Both hGAL-(1-30) and -(3-30) potentiated the rise in GHRH-stimulated GH levels [area under the curve (AUC), saline, 2,810 +/- 500 vs. hGAL-(1-30), 4,660 +/- 737, P < 0.01; vs. hGAL-(3-30), 6, 870 +/- 1,550 ng. min. ml(-1), P < 0.01]. In contrast to hGAL-(1-30), hGAL-(3-30) had no effect on basal GH levels (AUC, saline, -110 +/- 88 vs. hGAL 1-30, 960 +/- 280, P < 0.002; vs. hGAL-(3-30), 110 +/- 54 ng. min. ml(-1), P = not significant). These data suggest that the effects of galanin on basal and stimulated GH release are mediated via different receptor subtypes and that the human equivalent of GAL-R(W) may exist.     

Growth hormone releasing hormone receptors on thymocytes and splenocytes from rats.

In the present study, we determined that rat mononuclear leukocytes possess specific receptors for growth hormone releasing hormone (GHRH). The results show that the binding of 125I-labeled GHRH to spleen and thymic cells was saturable and of a high affinity, approximately 3.5 and 2.5 nM for thymus and spleen cells, respectively. The Scatchard analysis revealed a binding capacity of approximately 54 and 35 fmol per 10(6) cells on thymus and spleen, respectively. The binding of GHRH was not competed by 10(-6) M growth hormone, corticotropin releasing factor, substance P or luteinizing hormone releasing hormone and vasointestinal peptide (VIP). Partial characterization of the receptor was accomplished by crosslinking 125I-labeled GHRH to thymus cells with disuccinimidyl suberate and polyacrylamide gel electrophoresis. Autoradiography of dried gels showed two major components in leukocytes and pituitary cells at approximately 42 and 27 kDa which could be diminished by unlabeled GHRH. The treatment of leukocytes with GHRH (10 nM) rapidly increased the intracellular free calcium concentration from a basal level of 70 +/- 20 nM to a plateau value of 150 +/- 20 nM in 6 min after stimulation. The functional activity of GHRH receptors was studied further by measuring lymphocyte proliferative responses and the increase in the level of cytoplasmic GH RNA. The presence of GHRH alone resulted in a dose-dependent increase in thymidine and uridine incorporation and a dose-dependent increase in the levels of GH RNA in the cytoplasm. Taken together, the results show that lymphocytes contain specific receptors for GHRH that are coupled to important biological responses and further support the concept of bidirectional communication between the immune and neuroendocrine tissues.     

The effect of growth hormone administration on lipids and lipoproteins in growth hormone-deficient patients

Plasma lipids, lipoproteins, and lipoprotein cholesterol levels were studied in a group (n = 8) of prepubertal growth hormone-deficient patients before and after growth hormone (GH) administration. Determination of plasma lipoproteins by a sensitive agarose gel electrophoretic technique demonstrated: (a) in the patients with two prebeta bands an intensification of the fast prebeta lipoprotein fraction after growth hormone administration; and (b) in the patients with one prebeta band the appearance of a second prebeta band after growth hormone administration. The mean (+/- SD) plasma triglyceride level before GH was 86 +/- 60 mg/dl and 158 +/- 95 mg/dl after GH (P less than 0.01). Mean (+/- SD) plasma cholesterol level before GH was 196 +/- 25 mg/dl and 174 +/- 28 mg/dl after GH (P less than 0.05). High-density lipoprotein cholesterol concentrations decreased significantly (P less than 0.001) from mean (+/- SD) 55 +/- 12 mg/dl before GH to 37 +/- 10 mg/dl after GH. Very-low-density lipoprotein cholesterol concentrations increased significantly (P less than 0.05) from mean (+/- SD) 13 +/- 12 mg/dl before GH to 23 +/- 15 mg/dl after GH. Low-density lipoprotein cholesterol concentrations decreased (N.S.) from mean (+/- SD) 123 +/- 15 mg/dl before GH to 114 +/- 15 mg/dl after GH. These lipid and lipoprotein changes could be mediated through the insulin antagonism, hyperinsulinemia, and a decrease in lipoprotein lipase activity caused by growth hormone.     

Effects of acute and chronic methylphenidate administration on beta-endorphin, growth hormone, prolactin and cortisol in children with attention deficit disorder and hyperactivity

The effect of 5 mg/p.o. methylphenidate (MPH) challenge on beta-endorphin (beta-EP), growth hormone (GH), prolactin (Prl) and cortisol was investigated in 16 children suffering from attention deficit disorder with hyperactivity (ADDH) before and after 4 weeks MPH treatment. The study population consisted of 13 males and 3 females aged 6-11 years. All patients were drug free for at least 3 months prior to investigation. The severity of ADDH symptomatology and response to MPH chronic treatment was assessed using parent/teacher abbreviated Conners rating scale. Blood samples for beta-EP, cortisol, Prl and GH were drawn before initiation of treatment (basal pre-treatment level), 2 hours after MPH challenge, 4 weeks after MPH treatment (basal post-treatment level) and 2 hours after re-challenge with MPH. Chronic MPH treatment resulted in a decrease in basal Prl levels (5.5 +/- 2.8 vs 3.7 +/- 1.9 ng/ml; p less than 0.05). Pre-treatment challenge stimulates significantly both beta-EP (15.0 +/- 7.5 vs 12.5 +/- 5.3 pmol/l; p less than 0.05) and cortisol secretion (20.6 +/- 6.6 vs 12.6 +/- 5.8 micrograms/dl; p less than 0.05), and suppressed Prl secretion (4.0 +/- 1.5 vs 5.5 +/- 2.8 ng/ml; p less than 0.05). Re-challenge with MPH enhanced beta-EP levels (14.9 +/- 8.6 vs 10.6 +/- 5.0 pmol/l; p less than 0.05) but failed to affect cortisol, Prl and GH secretion. The acute and chronic neuroendocrine effects of MPH administration might be related to its dopaminergic and adrenergic agonistic activity. It might be that the stimulatory effect of single and repeated acute MPH administration on beta-EP release contributes to the beneficial effect of MPH treatment in ADDH children.     

Growth hormone response to human pancreatic growth hormone releasing factor in cattle

The effects of a growth hormone releasing factor, human pancreatic growth hormone releasing factor-44 (hpGRF-44), on growth hormone (GH) secretion in calves, heifers and cows were studied. A single intravenous (iv) injection of 0.1, 0.25, 0.5 or 1.0 microgram of synthetic hpGRF-44 per kg of body weight (bw) in calves significantly elevated the circulating GH level within 2-5 min, while no increase in plasma GH was observed in saline injected control calves. The plasma GH level increased proportionally to the log dose of hpGRF-44, and reached a peak at 5-10 min (p less than 0.01). Subcutaneous injection of hpGRF-44 also elevated the plasma GH level, but the peak value at 15 min was 37% of that of iv injection (p less than 0.05). Intravenous injection of 0.25 microgram of hpGRF-44 per kg of bw to female calves, heifers, and cows significantly elevated mean the GH levels from 8.5, 2.3, and 1.6 ng/ml at 0 time to peak values of 97, 26, and 11.6 ng/ml, respectively (p less than 0.01). The plasma GH response and basal level in calves were significantly higher than those of heifers or cows (p less than 0.025). The plasma GH response to hpGRF-44 as well as the basal level decreased with advancing age. The plasma GH response to hpGRF-44 and basal GH in male calves were significantly greater than those in female calves (p less than 0.001). These results indicate that synthetic hpGRF-44 is a potent secretogogue for bovine GH, and suggest its usefulness in the assessment of GH secretion and reserve in cattle.     

The episodic secretory pattern of growth hormone regulates liver carbonic anhydrase III. Studies in normal and mutant growth-hormone-deficient dwarf rats.

Carbonic anhydrase III (CAIII) occurs in male rat liver at concentrations twenty times those in the female, and is sensitive to the pattern of growth hormone (GH) release. Males release GH episodically and have high concentrations of CAIII; females produce GH in a more continuous fashion and have lower CAIII levels. In normal female rats, the endogenous GH secretory pattern was masculinized, either by regular injections of GH-releasing factor (GRF) or by intermittent infusions of somatostatin (90 min on/90 min off). Both treatments induced regular GH pulses and stimulated growth, but only intermittent somatostatin infusions raised CAIII levels (controls, 1.5 +/- 0.5; somatostatin-treated, 9.0 +/- 2.9 micrograms/mg; means +/- S.D.). GRF pulses (4 micrograms every 4 h) did not however raise CAIII levels (controls 1.8 +/- 0.5; GRF-treated 1.4 +/- 0.4 micrograms/mg). Surprisingly, hepatic CAIII is also sexually dimorphic (males, 18.8 +/- 3; females, 2.22 +/- 0.4 micrograms/mg) in a GH-deficient dwarf rat strain which has low plasma GH levels without 3-hourly GH peaks. Intermittent somatostatin infusions in female dwarf rats partially masculinized hepatic CAIII, an effect reduced by co-infusion with GRF. This CAIII response was not secondary to growth induction, since neither somatostatin nor GRF stimulated growth in dwarf rats, and pulses of exogenous GH stimulated growth in female dwarfs without masculinizing CAIII levels. Furthermore, continuous GH infusion in male dwarf rats partially feminized hepatic CAIII levels (to 9.1 +/- 2.4 micrograms/mg), whereas infusions of insulin-like growth factor-1, which induced the same body weight gain, did not affect hepatic CAIII (20.8 +/- 6 micrograms/mg). These results show that hepatic CAIII expression is highly sensitive to the endogenous GH secretory pattern, independent of growth. They also implicate the low basal GH levels between pulses, rather than the peak GH levels, as the primary determinant of the sexually dimorphic hepatic CAIII expression in the rat.     

The molecular weight forms of rat growth hormone secreted in response to growth hormone-releasing factor

The different molecular weight forms of immunoreactive growth hormone (irGH) secreted by the anterior pituitary of rats were evaluated during basal and stimulated secretion in vitro and in vivo. Anterior pituitary cells maintained in a monolayer culture system secreted only a 22,000-Da form of GH based on Sephacryl S-200 column chromatography. This was also true for the irGH secreted in response to growth hormone-releasing factor and prostaglandin E2 stimulation. In contrast, the molecular weight forms of irGH found in plasma under basal conditions included an approximately 90,000-Da form as well as the expected 22,000-Da form. The concentrations of both forms increased following growth hormone-releasing factor stimulation although there was a shift in the ratio of the forms secreted. These results suggest that the larger molecular weight forms of rat GH observed in plasma may be the result of some postsecretory process which occurs in blood and suggests a possible regulatory function for the larger molecular weight forms as it pertains to the bioavailability of GH in vivo.     

Secretory bursts of growth hormone secretion in the dog may be initiated by somatostatin withdrawal

In 28 6-h experiments on 10 conscious resting trained male dogs, plasma growth hormone (GH) was determined at 5-min intervals by radioimmunoassay. For all experiments, the basal GH concentration in plasma was 0.80 +/- 0.06 ng mL-1. In each experiment, 1-3 secretory bursts of GH occurred, raising plasma GH 2.4 to 15.3 times basal concentrations (for all 43 bursts, 6.6 +/- 0.4 times the basal value). Metabolic clearance rates (MCR) and apparent distribution volumes (V) were determined, using stepwise infusions of canine GH. The MCR (3.99 +/- 0.30 mL kg-1 min-1) and V (57.9 +/- 5.5 mL kg-1) were used to transform the GH concentration versus time data into GH secretion rates, using a single compartment approach. Basal GH secretion rates for all 28 experiments were 3.12 +/- 0.24 ng kg-1 min-1. The secretory bursts yield peak GH secretion rates of 9.4 +/- 0.8 times basal secretion and these steep-sloped bursts last 25.1 +/- 1.2 min. Six-hour infusions of 0.15 microgram kg-1 min-1 of somatostatin (SRIF) abolished all secretory bursts but did not lower basal secretion rates. In five of seven SRIF infusion experiments in which samples were taken after the infusion ceased a secretory burst was seen in the hour following cessation of infusion (in four cases within 10 min). These secretory bursts lasted 23.0 +/- 2.9 min and were similar to those seen in control experiments. Infusions of SRIF at 0.05 microgram kg-1 min-1 had no effect. These results imply that during basal GH secretion, a surfeit of SRIF impinges on the somatotrophs, as extra SRIF does not further lower basal secretion. However, during secretory bursts, very little SRIF must be present, as exogenous SRIF blocks these bursts. The bursts are similar in duration to overshoots provoked in perifused dispersed rat somatotrophs by removal of an SRIF signal. It seems likely that their cause in vivo is similar. (All values are means +/- SEM.)     

The effects of 5-azacytidine on the expression of the rat growth hormone gene. Methylation modulates but does not control growth hormone gene activity

The role of DNA methylation in the expression of the rat growth hormone (rGH) gene was assessed by using a hypomethylating agent, 5-azacytidine, and the iso-schizomeric restriction enzymes MspI and HpaII. 5-Azacytidine increased rGH mRNA 3-8-fold in GH3D6 cells, a subclone of rat pituitary tumor cell lines that expresses one-tenth to one-fifteenth the GH expressed by two other clones, GH3 and GC. The effect was also detected at the level of pre-mRNA. The effect was independent of glucocorticoids and thyroid hormones and was found to be inheritable. The DNA methylation pattern generated by the isoschizomeric restriction enzymes indicated that the HpaII sites in the rGH gene were mostly methylated in GH3D6 cells but mostly unmethylated in GC cells. After treatment with 5-azacytidine, about 22% of these HpaII sites in GH3D6 cells became unmethylated. Thus, DNA methylation correlates inversely with the expression of the rGH gene in these cell lines. However, three other observations indicate that factors in addition to DNA methylation control rGH expression. First, in GC cells, even though most of the HpaII sites are unmethylated, the gene is not fully expressed. Second, in rat hepatoma cells, which do not express GH at all, the GH gene is less methylated than that in GH3D6 cells. Third, within the sensitivities of the assay methods, 5-azacytidine has no effect on the GH gene when it is completely silent. Taken together, the findings indicate that DNA methylation modulates but does not control GH gene expression. It is tempting to speculate that DNA methylation can influence expression only when the gene is committed to express.     

Study of insulin-like growth factor I in human obesity.

In obesity there is a decrease in basal and stimulated GH secretion. IGF-I, which has negative feedback effects on GH secretion, could be the initial mediator of such alterations. We studied IGF-I levels in obese subjects and their relationship to the obesity level and GH secretion. We determined plasma IGF-I, basal and stimulated GH in 30 normal and 30 obese women and related these variables to obesity indices (body mass index, BMI, and % overweight). Baseline plasma GH values were 1.2 +/- 0.3 and 2.3 +/- 0.6 micrograms/l in obese subjects and controls, respectively (NS). Mean peak GH secretion after stimuli were 11.2 +/- 1.4 and 34.4 +/- 5.6 micrograms/l in obese subjects and controls, respectively (p less than 0.001). Plasma IGF-I were 1.0 +/- 0.1 U/ml and 0.7 +/- 0.1 U/l in obese subjects and controls, respectively (NS). There was a significant negative correlation between plasma IGF-I and age (r = -0.55, p less than 0.001) and a significant negative correlation between mean peak GH secretion and weight (r = -0.60, p less than 0.001), BMI (r = -0.64, p less than 0.001) and percentage of ideal body weight (r = -0.67, p less than 0.001). We did not find any correlation between IGF-I and indices of overweight. These data suggest that the reduced GH secretion found in obesity is not related to a negative feedback inhibition by elevated levels of IGF-I and that adiposity is not associated with a decline in IGF-I levels. We confirm the existence of a negative correlation between GH secretion and obesity indices.     

Growth hormone response to a bolus injection of 1-44 growth-hormone-releasing hormone in very short children with intrauterine onset of growth failure

The release of growth hormone (GH) during the 120 min following a bolus venous injection of 1-44 GH-releasing hormone (GHRH) 2 micrograms/kg was studied in 52 prepubertal children aged 8.4 +/- 2.1 years, having a nonfamilial growth deficiency of prenatal onset (-3.26 +/- 1.13 SDS at birth, -3.22 +/- 0.88 SDS at the time of study) and a normal response to conventional GH stimulation tests. GH release reached a peak level of 96.1 +/- 60.2 microU/ml, being significantly higher than that found in 68 non-GH-deficient very short children whose growth failure had a postnatal onset, and not significantly correlated with the response to conventional tests. 26 of the 52 intrauterine growth retardation (IUGR) patients were re-tested with GHRH in similar conditions after 6-12 months of daily subcutaneous injections of GH and 2 days without. They reached at the second test a peak plasma GH level of 91.7 +/- 56.1 microU/ml, not different from their response to the first test. These data could be taken into consideration for long-term studies of the clinical effects of GH in IUGR children with persisting severe growth deficiency.