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Biomedical subjects

M Cappa

Publications and source records attributed to M Cappa.

At least 37 records · Page 2Linked to original sources
PubMed1998

The growth hormone response to hexarelin in patients with Prader-Willi syndrome.

Hexarelin (Hex) is a synthetic hexapeptide with potent GH-releasing activity in both animals and men. Aim of this study was to evaluate the GH response to a maximal dose of Hex and GH-releasing hormone (GHRH) in a group of patients with Prader-Willi syndrome (PWS). Seven patients (4 boys and 3 girls, age 2.4-14.2 yr) with PWS, 10 prepubertal obese children (7 boys and 3 girls, age 7.5-12.0 yr), and 24 prepubertal short normal children (11 boys and 13 girls, age 5.9-13 yr) with body weight within +/- 10% of their ideal weight were studied. All subjects were tested on two occasions with GHRH 1-29 at the dose of 1 microgram/Kg i.v., and with Hex at the dose of 2 micrograms/Kg i.v. In the PWS patients the GH response to GHRH (peak = 6.4 +/- 2.0 micrograms/l, p < 0.0001; AUC = 248 +/- 70 micrograms min/l, p < 0.0001) was significantly lower than that observed in the short normal children and similar to that observed in the obese children. In the PWS children the GH response to Hex (peak = 7.5 +/- 1.6 micrograms/l; AUC = 309 +/- 53) was similar to that observed after GHRH and significantly lower than that observed in the obese children (p < 0.05). The results of this study show that PWS patients have a blunted GH response to the administration of a maximal dose of Hex. Whether these findings reflect a more severe pituitary GH deficiency in PWS than in obese children or a deranged hypothalamic regulation of GH secretion need further investigation.

Adolescent↗
PubMed1998

Altered bone mineral density in patients with complete androgen insensitivity syndrome.

Androgens have major influences on the regulation of bone mineralization. Because of their unique peripheral metabolism androgens may act on bone via activation of the androgen and/or estrogen receptor. Patients with complete androgen insensitivity syndrome (cAIS) are natural models to assess androgen actions on bone. We studied bone mineral density (BMD) in 10 patients with cAIS (mean age 13.70, range 4.7-19.8 years); 3 patients were studied before gonadectomy; the others were castrated and 6 were on hormonal replacement therapy. The BMD area (aBMD) was measured by dual energy X-ray; lumbar 'apparent' volumetric density (vBMD) was calculated using the formula vBMD = aBMD x [4/(pi x width)]. In the patients, aBMD (0.72 +/- 0.16 g/cm2) and vBMD (0.23 +/- 0.04 g/cm3) were significantly (p < 0.001) reduced in comparison with those of a control group (n = 15, age 5.0-20.5 years: aBMD 1.028 +/- 0.20 g/cm2; vBMD 0.35 +/- 0.04 g/cm3). Both aBMD and vBMD were also reduced in comparison with normal values for males (aBMD -2.66 +/- 0. 99 SDS, p < 0.001; vBMD -3.08 +/- 1.53 SDS, p < 0.0005) and females (aBMD -2.88 +/- 1.05 SDS, p < 0.001; vBMD -2.84 +/- 1.18 SDS, p < 0. 0007). Real lumbar bone density, assessed by computed tomography in 1 patient, was also reduced (-6.2 SDS and -3.5 SDS for male and female normal values, respectively). Biochemical markers of bone metabolism were normal and not significantly different in patients and controls. Girls with cAIS did not have more fractures than controls. In conclusion, both aBMD and vBMD are reduced in cAIS patients, while bone turnover and the fracture risk seem not to be increased. Our data indicate that both androgens and estrogens may be required for acquisition of bone density during childhood.

Absorptiometry, Photon↗
PubMed1998

The growth hormone response to hexarelin in patients with different hypothalamic-pituitary abnormalities.

We evaluated the GH-releasing effect of hexarelin (Hex; 2 microg/kg, i.v.) and GHRH (1 microg/kg, i.v.) in 18 patients (11 males and 7 females, aged 2.5-20.4 yr) with GH deficiency (GHD) whose hypothalamic pituitary abnormalities had been previously characterized by dynamic magnetic resonance imaging (MRI). Ten patients had isolated GHD, and 8 had multiple pituitary hormone deficiency. All patients were receiving appropriate hormone replacement therapy. Twenty-four prepubertal short normal children (11 boys and 13 girls, aged 5.9-13 yr, body weight within +/-10% of ideal weight) served as controls. MRI studies revealed an ectopic posterior pituitary at the infundibular recess in all patients. A residual vascular component of the pituitary stalk was visualized in 8 patients with isolated GHD (group 1), whereas MRI showed the absence of the pituitary stalk (vascular and neural components) in the remaining 10 patients (group 2), of whom 8 had multiple pituitary hormone deficiency and 2 had isolated GHD. In the short normal children, the mean peak GH response to GHRH (24.8 +/- 4.4 microg/L) was significantly lower than that observed after Hex treatment (48.1 +/- 4.9 microg/L; P < 0.0001). In the GHD patients of group 2, the mean peak GH responses to GHRH (1.4 +/- 0.3 microg/L) and Hex (0.9 +/- 0.3 microg/L) were similar and markedly low. In the patients of group 1, the GH responses to GHRH (8.7 +/- 1.3 microg/L) and Hex (7.0 +/- 1.3 microg/L) were also similar, but were significantly higher that those observed in group 2 (P < 0.0001). In the whole group of patients, a significant correlation was found between the GH peaks after Hex and those after GHRH (r = 0.746; P < 0.0001). In this study we have confirmed that the integrity of the hypothalamic pituitary connections is essential for Hex to express its full GH-releasing activity and that Hex is able to stimulate GH secretion in patients with GHD but with a residual vascular component of the pituitary stalk.

Adolescent↗
PubMed1998

Prolactinomas in children and adolescents. Clinical presentation and long-term follow-up.

In this study, we report the clinical presentation, response to medical treatment, and long-term follow-up of 26 patients with prolactinoma (15 macro- and 11 micro-adenomas) diagnosed at the age of 7-17 yr. All patients were first treated with bromocriptine (BRC) at doses ranging from 2.5-20 mg/day orally. BRC was discontinued for intolerance and/or resistance to the drug and was replaced by quinagolide (CV) at doses ranging from 0.075-0.6 mg/day or by cabergoline at doses ranging from 0.5-3.5 mg/week orally. Two patients received external conventional radiotherapy after surgery. In 7 prepubertal males and 6 females with macroprolactinoma, headache and/or visual defects were the first symptoms. All females presented with primary or secondary amenorrhea. Growth arrest was observed in a male patient with microadenoma, whereas all the remaining patients had normal heights, and pubertal development was appropriate for their age. Spontaneous or provocative galactorrhea was observed in 12 patients (3 males and 9 females) and gynecomastia in 4 males. Mean serum PRL concentration (+/-SE) at the time of diagnosis was 1080 +/- 267 microg/L in patients with macroadenoma and 155 +/- 38 microg/L in patients with microadenoma. In 10 patients, BRC normalized PRL levels and caused variable, but significant, tumor shrinkage. CV normalized PRL concentrations and reduced tumor size in 5 patients. Cabergoline normalized PRL concentrations in 7 of 10 patients resistant to CV. Pregnancy occurred in 2 patients while on treatment. Pregnancies were uncomplicated, and the patients delivered normal newborns at term. Only 4 patients are still moderately hyperprolactinemic. Impairment of other pituitary hormone secretion was documented at the time of diagnosis in 7 patients, 5 of whom underwent surgery. Four patients became GH deficient in adult age. In conclusion, the medical treatment with dopaminergic compounds is effective and safe in patients with prolactinoma with onset in childhood, allowing preservation of the anterior pituitary function.

Adolescent↗
PubMed1997

Abnormalities of somatosensory and motor evoked potentials in adrenomyeloneuropathy: comparison with magnetic resonance imaging and clinical findings.

We studied 6 patients with adrenomyeloneuropathy (AMN) showing mild signs of central nervous system involvement. All patients underwent brain and spinal magnetic resonance imaging (MRI) and somatosensory (SEP) and motor (MEP) evoked potential study. Whereas SEPs and MEPs were abnormal in all patients, only 1 patient showed brain MRI abnormalities; spinal MRI showed hypotrophy without focal abnormalities in 4 of 6 patients. Median nerve SEPs, which were recorded with noncephalic reference montage, revealed delayed or absent scalp P14 far-field potential in all patients and abnormal spinal N13 in 2. Moreover, tibial nerve SEPs revealed abnormalities of the subcortical P30 response in all 4 patients in whom scalp-to-ear recording was employed. These findings strongly suggest that in the early stages of disease neurological dysfunction is localized in the spinal cord, where it is difficult to assess using MRI. However, SEPs and MEPs, which show a typical pattern of abnormality in these patients, could be useful in disclosing signs of long tract involvement and in monitoring treatment.

Adrenoleukodystrophy↗
PubMed1997

Growth hormone (GH) response to GH-releasing hormone in short children: lack of correlation with endogenous nocturnal GH secretion.

The growth hormone (GH) response to iv administration of GH-releasing hormone (GHRH, 0.3 microgram/Kg) was evaluated in 21 short children (13 boys and 8 girls, age 6.7-13.8 yr). Fourteen had familial short stature and/or constitutional growth delay, one had coeliac disease, and 6 were ultimately diagnosed as non-classical GH deficiency or neurosecretory dysfunction on the basis of subnormal integrated spontaneous GH concentrations (ICGH). The response was compared with 12-h spontaneous GH secretion measured every 30 min from 20:00 to 08:00. Mean ICGH ranged from 2.0-17.7 micrograms/l, with a maximum nocturnal GH peak ranging from 5.4-74 micrograms/l. The maximum GH peak after GHRH ranged from 9.4-50 micrograms/l, and the area under the curve (AUC) from 406-3012 micrograms.min/l. No correlation was found between the maximum GH peak and the AUC after GHRH and the maximum overnight GH peak, the ICGH and the overnight AUC. This study confirms that the GH response to GHRH is highly variable among short children with a wide range of spontaneous GH secretion, and that this response is not correlated with the spontaneous ability to secrete GH.

Adolescent↗
PubMed1997

Unilateral cryptorchidism corrected in prepubertal age: evaluation of sperm parameters, hormones, and antisperm antibodies in adult age.

OBJECTIVE: To evaluate whether prepubertal orchidopexy for unilateral cryptorchidism can reduce adult dysspermia. DESIGN: Patient follow-up comparison with control groups. SETTING: Surgical and endocrinologic sections of a children's hospital and a university infertility-care center. PATIENT(S): Seventy-one patients with unilateral cryptorchidism who underwent orchidopexy in prepubertal age (6.4 +/- 2.8 years) were followed up as adults (20.0 +/- 2.8 years). MAIN OUTCOME MEASURE(S): Patients underwent testicular examination and hormonal evaluation, 49 of these had semen analysis and antisperm antibody tests. Semen results were compared with those of two age-matched control groups: a group of 20 healthy, randomly selected subjects and a group of 20 patients operated on in postpubertal age for cryptorchidism. RESULT(S): Unilateral reduced testis size was found in 30.1% of patients, eight patients had a low LH level, eight had a low T level, and none had abnormal FSH values. Antisperm antibodies were found in 1 of 49 cases. Cluster analysis of sperm parameters showed that the mean values of patients were worse than those of the healthy controls but better than those of the subjects operated on in postpubertal age. CONCLUSION(S): This study indicates that prepubertal orchidopexy can given better results than postpubertal correction.

Adult↗
PubMed1997

Effects of exogenous hexacosanoic acid on biochemical myelin composition in weaning and post-weaning rats.

X-linked Adrenoleukodistrophy (ALD) is characterized by an increase of very long chain fatty acids (VLCFA) in particular of hexacosanoic acid (HA), in tissues and fluids. The biochemical abnormality is due to the dysfunction of peroxisomal degradation of VLCFA. To-date it is unclear if the demyelination which characterizes this disease is the direct consequence of HA accumulation. In order to investigate whether the large amounts of exogenous HA could affect myelin synthesis, 500 micrograms of this fatty acid dissolved in peanut oil were administered daily and by gavage to newborn rats. Since myelin is actively synthesized during early neonatal life and it can be altered by environmental factors including diet, we analyzed lipid and protein composition of myelin after 20, 30 and 60 days of HA administration. Our results show that exogenous HA is incorporated in myelin where it determines biochemical alterations in normal rats having a functioning peroxisomal system. Even though the differences between controls and treated rats are slight, we observed in test rats, a decrease of 2'3'-cyclic nucleotide 3'-phosphohydrolase (CNPase) activity and of myelin basic protein (MBP) content at any time studied. The decrease of glycolipids (GL) was present only after 20 days of treatment. Since these parameters are related to myelin development, our data lead us to think that the myelin of the treated animals is less mature than that of controls.

Animals↗
PubMed1997

Acute administration of hexarelin stimulates GH secretion during day and night in normal men.

OBJECTIVE: Hexarelin is a synthetic hexapeptide with potent GH-releasing activity in both animals and men. The aim of this study was to investigate the effect of a bolus injection of hexarelin given in the morning during wakefulness and during nocturnal sleep in a group of normal adult men. DESIGN AND SUBJECTS: Eight normal men, aged 21-33 years, of normal height and within 10% of ideal body weight were studied. All subjects received in random order saline or hexarelin (2 micrograms/kg) in the morning between 0800 and 0900 h after they had fasted overnight. The same experiments were performed during nocturnal sleep in the same subjects. Saline or hexarelin were injected within 30 minutes after the onset of sleep between 2300 and 2400 h. Sleep was recorded by visual inspection. MEASUREMENTS: In all four test sessions blood samples were taken 30, 15 minutes and immediately before the injection of saline or hexarelin and then every 15 minutes for 2 hours. GH was measured by an immunoradiometric assay. All values are expressed as peak GH levels or as area under the curve (AUC) calculated by trapezoidal integration. RESULTS: Mean peak GH concentrations after hexarelin during the morning (58.2 +/- 4.7 micrograms/l) (GH micrograms/l l x 2 = mU/l) were not different from those observed during sleep (61.2 +/- 4.3 micrograms/l). The rate of disappearance of GH from plasma was slower during sleep (t1/2 = 64.9 +/- 14.8 min) than during morning hours (t1/2 = 24.9 +/- 1.4 min, P < 0.01). Mean AUC responses to hexarelin during sleep (1466 +/- 145 micrograms.min/l) were significantly higher than during morning hours (903 +/- 94 micrograms.min/l, P < 0.001). CONCLUSIONS: These results show that GH responsiveness to a growth hormone releasing peptide is preserved during the night. This could be exploited for diagnostic and/or therapeutic purposes.

Adult↗
PubMed1997

Neurophysiological abnormalities in adrenoleukodystrophy carriers. Evidence of different degrees of central nervous system involvement.

We studied 19 women, heterozygous for adrenoleukodystrophy (ALD) in whom the carrier status was demonstrated by abnormally high plasma levels of very-long-chain fatty acids. Clinical examination revealed slight neurological signs in two patients. Clear-cut neurological deficits in three, and it was fully normal in the remaining 14. All subjects underwent motor evoked potential (MEP) and somatosensory evoked potential (SEP) studies. Seventeen out of 19 subjects underwent brain MRI which demonstrated various degrees of abnormality in one asymptomatic and five symptomatic subjects; SEPs and MEPs revealed CNS involvement in 12 and 8 out of the 19 subjects, respectively. Symptomatic patients showed severe neurophysiological abnormalities, whereas milder but unequivocal EP abnormalities were found in seven of the 14 patients with normal clinical examination. Our data thus suggest CNS involvement in the majority of the ALD carriers, evident also in preclinical stages and progressively severe. The possibility of assessing different degrees of neurological involvement could be relevant for therapeutical purposes. Moreover, neurophysiological studies could provide the only objective marker of functional nervous system involvement, e.g. in order to monitor the efficacy of treatment, and in clinically and radiologically silent cases.

Adolescent↗
PubMed1997

Long-term outcome of male-limited gonadotropin-independent precocious puberty.

Long-term outcome of five new cases of male-limited precocious puberty (MPP) is reported. Three patients had positive family history. One patient was untreated; 2 boys received cyproterone acetate (2.0-3.6 mg/kg/daily) without clinical effects. Two patients were treated with ketoconazole (600 mg/daily); in 1, GnRH analogue therapy (Buserelin, 1,600 microg/day) was added after 6 months of effective ketoconazole treatment for development of central precocious puberty. The other patient did not develop central puberty under ketoconazole treatment and improved his predicted adult height from 172.4 to 181.1 cm. Four patients reached final height [B.A. (therapy cyproterone acetate): age 22.0 years, -2.0 SDS; B.G. (untreated): age 15.5 years, -1.7 SDS; M.M. (therapy cyproterone acetate): age 19.5 years, -1.6 SDS; M.F. (therapy ketoconazole plus GnRH analogue): age 21.3 years, -2.2 SDS]; three had reduced testicular volume (B.A.: -1.6/-1.6 SDS; B.G.: -2.1/-2.1 SDS; M.F.: -2.4/-1.9 SDS); one (M.F.) showed oligospermia. We concluded that in MPP cyproterone acetate treatment did not improve final height; ketoconazole was effective in reducing testosterone secretion, but its real effect on final height cannot be determined; the timing of central puberty may be precocious, suggesting that an adjunctive GnRH analogue treatment may be needed. In some patients, testicular impairment may be present in young adulthood.

Androgen Antagonists↗
PubMed1997

The growth hormone response to hexarelin in children: reproducibility and effect of sex steroids.

We studied the variability of the GH response to the synthetic hexapeptide hexarelin (Hex) and the effect of sex steroids on the GH-releasing effect of Hex in a group of prepubertal short normal children. Twenty-five children were tested on two occasions 3-7 days apart with 2 micrograms/kg, i.v., Hex. The GH response to Hex was reevaluated after testosterone (T) administration in 10 boys, after ethinyl estradiol (EE) administration in 15 children (5 boys and 10 girls), and after oxandrolone (Ox) administration in 8 boys. In the 25 children tested twice, the mean GH peak and mean area under the curve after the first and second tests were similar. The mean (+/- SD) coefficients of variation of the GH peak and area under the curve responses to Hex was 22.7 +/- 21.0% and 24.0 +/- 20.7%, respectively. Priming with T and EE resulted in an increased GH response to Hex [41.8 +/- 21.0 before vs. 71.1 +/- 28.3 after T (P < 0.001); 43.0 +/- 14.5 before vs. 60.0 +/- 20.0 after EE (P < 0.005)], whereas Ox administration had no effect on the Hex-induced GH release. These data confirm that Hex is a potent stimulus for GH secretion in children with a limited intraindividual variability. In addition, we have shown that both T and EE, but not Ox, significantly augment the GH-releasing effect of Hex. Our data suggest that the sex steroid-induced increase in the GH response to Hex is mediated by estrogens.

Adolescent↗
PubMed1996

Clinical and roentgenographic findings in a patient with primordial microcephalic dwarfism type Caroline Crachami.

We describe a patient with primordial microcephalic dwarfism with severe intrauterine growth retardation and severe and progressive postnatal deficit in length, weight and head circumference. The patient was extroverted and sociable but mildly mentally retarded. He had marked delay of bone maturation and an enlargement of the sella turcica. This child and two previously reported patients [Boscherini et al., Eur J Pediatr 137:237-242, 1981] have many characteristics in common with Caroline Crachami, the famous "Sicilian dwarf". We think that these patients belong to a separate category of microcephalic primordial dwarfism.

Abnormalities, Multiple↗
PubMed1996

Pituitary-ovarian responses to leuprolide acetate testing in patients with congenital adrenal hyperplasia due to 21-hydroxylase deficiency.

To assess whether patients with congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency exhibit a steroidogenic response to GnRH agonist consistent with functional ovarian hyperandrogenism (FOH) and elucidate the relationship between adrenal and ovarian hyperandrogenism, the LH, FSH, estradiol, 17-hydroxyprogesterone (17-OHP), androstenedione, total testosterone, dehydroepiandrosterone, and 17-hydroxypregnenolone responses to a sc dose of leuprolide acetate (500 micrograms) were evaluated in 10 patients with classic CAH (mean age, 18.4 +/- 0.95 yr), 7 of whom had oligomenorrhea, pretreated with dexamethasone (2 mg/day for 5 days, including the day of the test). The results were compared with those obtained in 11 patients with FOH (mean age, 18.7 +/- 0.46 yr) and 17 normal women (mean age, 19.68 +/- 0.59 yr) not pretreated with dexamethasone. Leuprolide acetate stimulation caused a significant augmentation of plasma E2, 17-OHP, androstenedione, testosterone, and 17-hydroxypregnenolone concentrations in all CAH patients. However, in only 6 (60%) of them, all with oligomenorrhea, was the 17-OHP response (posttest minus pretest value) similar to that of FOH patients and significantly higher than that in controls. In this subset of CAH patients, LH plasma levels after stimulation were significantly higher than those of CAH subjects with 17-OHP responses in the normal range, controls, and FOH patients, whereas FSH levels were similar to those of controls. In this latter group, plasma FSH concentrations after stimulation were significantly higher than those in FOH. In conclusion, the results of the present study indicate that LH-dependent functional ovarian hyperandrogenism is frequent in patients with classic CAH. As ovarian hyperandrogenism might be partially responsible for the menstrual irregularities that are common complications in such patients, all classic CAH patients with oligomenorrhea should undergo short term stimulation with GnRH agonists to ascertain the presence of ovarian hyperandrogenism and receive appropriate treatment.

17-alpha-Hydroxypregnenolone↗
PubMed1996

Reliability of provocative tests to assess growth hormone secretory status. Study in 472 normally growing children.

The reliability of provocative stimuli of GH secretion in the diagnosis of GH deficiency is still controversial. Until now, normative values of GH response to various stimuli have not been established properly. In 472 children and adolescents with normal stature (n = 295, height SDS range -1.5 to 1.2) or normal short stature (n = 177, height SDS range -3.7 to -1.8), we studied the GH response to physical exercise, insulin-induced hypoglycemia, arginine (ARG), clonidine, levodopa, glucagon, pyridostigmine (PD), GHRH, PD + GHRH, and ARG + GHRH. The peak GH responses (range) to various stimuli were: 1) physical exercise: 3.0-28.3 micrograms/L; 2) insulin-induced hypoglycemia: 2.7-46.4 micrograms/L; 3) ARG: 0.5-48.4 micrograms/L; 4) clonidine: 3.8-86.0 micrograms/L; 5) levodopa: 1.9-40.0 micrograms/L; 6) glucagon: 1.9-49.5 micrograms/L; 7) PD: 2.5-35.0 micrograms/L; 8) GHRH: 2.7-102.7 micrograms/L; 9)PD + GHRH: 19.6-106.0 micrograms/L; and 10) ARG + GHRH: 19.4-120.0 micrograms/L. Our results show that all conventional stimuli of GH secretion frequently failed to increase GH levels, showing values lower than that arbitrarily assumed, so far, as minimum normal GH peak, i.e. 7 or 10 micrograms/L. When combined with PD or ARG (substances inhibiting hypothalamic somatostatin release), GHRH becomes the most powerful test to explore the secretory capacity of somatotrope cells (the GH response being always higher than 19 micrograms/L). Therefore, only GHRH combined with PD or ARG may be able to clearly differentiate normal children from patients with GH deficiency, though a normal GH response to these tests cannot rule out the existence of GH hyposecretory state because of hypothalamic dysfunction.

Adolescent↗
PubMed1996

Can provocative growth hormone testing predict the response to recombinant human growth hormone (rhGH) treatment?

Treatment with rhGH has been proven to be useful in children with chronic renal insufficiency and stunted growth. The aim of this study was to assess the usefulness of endocrinological provocative testing in predicting results to rhGH treatment. Endocrinological investigations performed in 14 children on renal replacement therapy did not correlate with increment of height velocity in the first year of rhGH therapy. It is concluded that no endocrinological testing is useful before starting rhGH treatment; other predictors of the response to rhGH administration are needed.

Adolescent↗
PubMed1995

Exogenous growth hormone administration does not inhibit the growth hormone response to hexarelin in normal men.

Administration of exogenous human growth hormone (GH) blunts the GH response to physiological as well as pharmacological stimuli, including GH-releasing hormone (GHRH). Hexarelin (Hex) is a new synthetic GH-releasing peptide (GHRP) similar to GHRP-6 with potent GH-releasing activity in animals and men. To determine whether the short-term administration of GH inhibits the Hex-induced GH release, we measured the GH response to Hex (2 micrograms/kg iv) in five normal adult males (age 26-32 yr) three h after an iv bolus of rhGH (2 IU) or saline. Mean incremental change of serum GH from value at time 0 was 47.5 +/- 5.5 and 41.5 +/- 4.1 micrograms/l after saline + Hex and GH + Hex, respectively. Mean incremental area under the curve over baseline was 3216 +/- 586 and 3735 +/- 506 micrograms.min.1 after saline + Hex and GH + Hex, respectively. One of the proposed mechanism of action of GHRPs is to serve as functional somatostatin (SRIH) antagonists, and it is known that GH feeds backs on the hypothalamus to stimulate SRIH release. Therefore, we speculate that antagonisms of SRIH function by Hex prevented the inhibitory effect of exogenous GH, thus lending further support to the hypotheses that SRIH is involved in the feedback regulation of GH secretion, and that GHRPs action involves inhibition of SRIH function.

Adult↗