THE EFFECT OF CALCITONIN ON GROWTH HORMONE SECRETION IN MAN

To determine whether human calcitonin inhibits GH secretion in man, as has been described for salmon calcitonin, the effect of an i.v. bolus of human calcitonin or saline on GH release after either insulin-induced hypoglycaemia or the administration of GH-releasing hormone (GHRH) or saline was studied. After the injection of calcitonin, no spontaneous GH surges were seen; the GH response to hypoglycaemia was diminished and the response to GHRH almost completely suppressed. Administration of calcitonin also caused a small and transient rise in plasma PRL and TSH but not LH levels, and no change in the integrated PRL or TSH response. Calcium and magnesium levels did not change. It is concluded that human calcitonin suppresses GH secretion in man, but not by suppressing GHRH and probably not by increasing somatostatin release. In addition, calcitonin has limited PRL and TSH-releasing activity.     

THE EFFECT OF METHANDROSTENOLONE ON PITUITARY GROWTH HORMONE SECRETION IN PREPUBERTAL CHILDREN

The effect of methandrostenolone on plasma growth hormone levels was studied in twenty-two apparently healthy prepubertal children (nineteen males and three females) with idiopathic growth retardation, following insulin hypoglycaemia (eight children) or arginine infusion (fourteen children). The tests were performed before and after 5 days or 34 months of peroral administration of methandrostenolone (0.1 54.33 or 0.03-0.05 mg/kg/day, respectively).     

EFFECT OF l-DOPA ON THE SECRETION OF PLASMA GROWTH HORMONE IN CHILDREN AND ADOLESCENTS

The stimulation of growth hormone release in children by L-dopa has been studied. An oral dose of 0.5 g L-dopa was administered to fourteen children with, and to fifteen children without, hypothalamic-pituitary insufficiency. In the control group, L-dopa induced a release of pituitary growth hormone, the peak of which occurred from 30 to 60 min after ingestion. Nine out of fifteen control subjects showed peak levels of plasma growth hormone greater than 8 ng/ml. None of the patients with hypothalamic-pituitary insufficiency showed levels greater than 5 ng/ml. In five out of six children with measurable amounts of plasma HGH, and in fourteen children with a lack of HGH, there was a good correlation between the HGH response after L-dopa, insulin hypoglycaemia and arginine infusion. It is concluded that the administration of one oral dose of L-dopa can be used as a provocative test of growth hormone secretion.     

THE EFFECT OF GALANIN ON BASELINE AND GHRH-INDUCED GROWTH HORMONE SECRETION IN OBESE CHILDREN

We have evaluated the effect of the administration of galanin (Gal), a newly identified hypothalamic peptide, on baseline and GHRH-induced GH rise in five obese children and in seven controls. The GH response to GHRH (hpGRF(1-29), 1 microgram/kg i.v.), and to Gal (15 micrograms/kg/h for 1 h), evaluated both as the maximum GH peak and as integrated area under the curve (AUC), was significantly lower in the obese children than in the controls. Simultaneous administration of Gal plus GHRH significantly increased the GH response to GHRH in all the obese subjects, so that their mean peak GH levels and AUC after Gal plus GHRH were similar to those of the control children after GHRH. Also, in control children Gal caused a significant augmentation of the GH response to GHRH. Mean peak GH levels and mean AUC after Gal plus GHRH were significantly higher in the controls than in the obese children given the same treatment. Our data indicate that obese children have a blunted GH response to Gal, which, however, is able to enhance the GH response to GHRH. This observation strengthens the view that the mechanism of action of Gal involves modulation of endogenous somatostatin (SRIH) release. In addition, similarity between the effects of Gal and pyridostigmine on baseline and GHRH-stimulated GH release in obese children may indicate the existence of a cholinergic link in the action of Gal.     

THE INFLUENCE OF OCTREOTIDE TREATMENT ON PULSATILE GROWTH HORMONE RELEASE IN ACROMEGALY

The pulsatile release of GH was investigated in eight active acromegalic patients before and during a subcutaneous infusion of 300 micrograms octreotide/24 h for 4 weeks. The number of GH pulses increased from a basal value of 14.4/24h to 16.3/24h during octreotide therapy. At the same time the mean GH concentration, valley concentration, peak height and amplitude decreased significantly. The inhibitory effect of octreotide on pulse characteristics did not depend on the time of day. IGF-I levels also decreased significantly; in five patients normal levels were reached. IGF-I levels correlated significantly with the mean GH level (r = 0.714, P less than 0.001), mean valley concentration (r = 0.697, P less than 0.001) and, to a lesser extent, area under the curve (r = 0.436, P = 0.033), but not the number of pulses. Plasma octreotide levels did not correlate with pulse parameters. In all but one patient a circadian rhythm was present during both the basal study and octreotide therapy. Compared with surgically treated acromegalics, the number of GH pulses was higher in untreated and octreotide-treated patients. This study demonstrates the pulsatile release of GH in active acromegaly both before and during octreotide therapy. This result suggests that endogenous GHRH is important for the generation of GH pulses in this disease.     

生长介素对肢端肥大症患者垂体瘤生长激素分泌影响的体外研究

作者在8例肢端肥大症体外培养的垂体GH瘤细胞上探讨IGF-1对GH分泌的反馈调节作用。10~(-7)mol IGF-1使3例垂体GH瘤细胞GH基础分泌抑制到对照的44.6％～52.4％(P<0.05),1例GH分泌增加134.9％(P<0.05),4例GH基础分泌没有明显改变,表明体外培养的垂体GH瘤有一半以上对IGF-1 3小的·的急性作用失去正常的GH分泌抑制反应。3例对IGF-1失去GH分泌抑制反应的垂体GH瘤细胞同时伴有GH对GHRH_(1-44)及(或)生长抑素激动剂SMS_(201-995)反应消失,提示部分垂体GH瘤细胞的IGF-1和某些下丘脑激素受体或受体后有异常。     

THE EFFECT OF SHORT- AND LONG-TERM CORTICOSTEROID TREATMENT ON SLEEP-ASSOCIATED GROWTH HORMONE SECRETION

Eight healthy medical studients and four renal transplant patients had blood sampled two or three times hourly throughout EEG monitored nocturnal sleep. This was carried out on the healthy subjects for a total of 12 nights without medication (control nights asleep), a total of 12 nights following 40 mg of flucortolone the previous morning, and a total of 6 nights with similar blood sampling when sleep was prevented (control nights awake). Four renal transplant patients who were receiving long-term therapy with prednisolone were similarly studied (total of 7 nights asleep). Circulating corticosteroid and growth hormone (GH) levels were determined. A peak of GH was seen during the first 2 h of sleep on the control nights when slow-wave sleep predominated. The GH peak was absent on the control nights awake. The pattern of plasma corticosteroid levels was identical during control nights asleep and awake. Both single-dose and chronic corticosteroid administration inhibited the GH peak associated with slow-wave sleep. Chronic corticosteroid therapy, but no single-dose administration in the morning, suppressed the circadian rise of plasma corticosteroids which normally occurs late in sleep.     

THE INTERACTION BETWEEN CLONIDINE AND GROWTH HORMONE RELEASING HORMONE IN THE STIMULATION OF GROWTH HORMONE SECRETION IN MAN

Six normal adult males were given clonidine and GHRH either separately, or in combination, in random order. The peak serum GH concentrations elicited by clonidine or GHRH were variable but one factor influencing the GH response to GHRH was the GH secretory status in the hour prior to the administration of the GHRH. Peak serum GH concentrations attained were significantly greater when serum GH concentrations were rising (mean 52.9 mU/l, SD 17.2) than if they were falling (mean 27.5 mU/l, SD 13.3) or unchanged/undetectable (mean 20.6 mU/l, SD 9.8) (one-way ANOVA, F = 8.77; P = 0.004). The GH response to clonidine was not influenced by the secretory status in the hour prior to administration of clonidine. Pretreatment with clonidine did not augment the peak serum GH response to GHRH but the direction of response was more predictable than when GHRH was administered separately or repeatedly. Prior treatment with GHRH(1-29)-NH2 led to a marked attenuation of the peak serum GH response to clonidine. These results suggest that the alpha-2 adrenergic agonists probably stimulate GH secretion through pathways other than just GHRH.     

OVERNIGHT URINARY GROWTH HORMONE MEASUREMENT IN THE DIAGNOSIS OF ACROMEGALY

Several studies report higher urinary GH excretion in acromegalic patients compared to control subjects. We investigated the diagnostic potential of overnight urinary GH excretion in acromegaly, using a recently developed enzyme-linked immunosorbent assay. Overnight urine samples were obtained from 117 control subjects and nine patients with untreated acromegaly. GH excretion was higher in acromegalic patients compared to control subjects, with geometric mean total overnight values of 46.35 and 5.73 microU respectively. The range for total overnight urinary GH in control subjects was 0.75-21.75 microU and two of the nine patients with untreated acromegaly had GH measurements within this range. Urinary GH measurements were corrected using predictive clinical variables but this resulted in minimal improvement in discrimination between control subjects and acromegalic patients. Lack of complete discrimination between control subjects and acromegalic patients limits the usefulness of a single overnight urinary GH measurement as a screening test for acromegaly.     

EFFECT OF SOMATOSTATIN ON ABNORMAL GROWTH HORMONE AND PROLACTIN SECRETION IN PATIENTS WITH THE CARCINOID SYNDROME

Growth hormone (GH) secretion has been studied in two patients with the carcinoid syndrome during glucose loading and growth hormone-release inhibiting hormone (GHRIH, somatostatin) infusion. Both patients had elevated fasting GH levels which were not suppressed by glucose; GH levels fell rapidly during GHRIH infusion. One patient also had hyperprolactinaemia with galactorrhoea and the prolactin (PRL) levels were unaltered by GHRIH. The association between carcinoid tumours and abnormalities of GH and PRL secretion is discussed.     

THE EFFECT OF OXANDROLONE ON THE GROWTH HORMONE RESPONSE TO GROWTH HORMONE RELEASING HORMONE IN CHILDREN WITH CONSTITUTIONAL GROWTH DELAY

The effect of treatment with oxandrolone, an anabolic steroid, on GH response to GH-releasing hormone (GHRH) has been evaluated in children with constitutional growth delay. Five subjects, four males and one female, aged 11.0-17.1 years were given oxandrolone 0.1 mg/kg p.o. daily for 2 months, and underwent acute administration of GHRH (GRF 1-40, 1 microgram/kg i.v.) before and after withdrawal of oxandrolone therapy. GHRH administration induced a much greater GH response, evaluated either as a peak plasma GH levels or plasma GH integrated area, after than it did before oxandrolone treatment. These findings indicate that in children with constitutional growth delay oxandrolone increases the sensitivity of somatotrophs to exogenous GHRH and, likely, to the endogenously-released neurohormone.     

THE EFFECT OF BROMOCRIPTINE ON INSULIN SECRETION AND GLUCOSE TOLERANCE IN PATIENTS WITH ACROMEGALY

The oral administration of bromocriptine 5 mg 6-hourly to twelve patients with acromegaly for a mean period of 12 (range 3–27) months significantly reduced whole blood glucose, plasma insulin and plasma growth hormone (GH) concentrations during a 50 g oral glucose tolerance test (OGTT). After this period of treatment, bromocriptine was withdrawn for 48 h resulting in a significant rise in whole blood glucose, plasma insulin and plasma GH concentrations during a repeat OGTT. It is concluded that bromocriptine therapy improves glucose tolerance in acromegaly by suppressing GH secretion and consequently GH-mediated antagonism of insulin.     

BROMOCRIPTINE SUPPRESSION OF PLASMA GROWTH HORMONE IN ACROMEGALY

Twelve acromegalic patients were studied in one or more of three protocols to establish the response of plasma growth hormone (hGH) concentraions to (a) a single oral test dose of bromocriptine, (b) incremental dose therapy from 10 mg/day to 40 mg/day over 4 weeks, and (c) sustained therapy with 20 mg/day over a 3 month period. Ten of the patients studied had previously been treated by yttrium implantation, external pituitary irradiation or surgical hypophysectomy. A high incidence of side effects including postural hypotension, hallucinations and peripheral vasospasm was noted reducing the numbers of patients completing the three protocols. Suppression of hGH concentrations was disappointing; significant reductions in hGH concentraions occurred in five of eleven patients in response to a single test dose of bromocriptine, and in only one of seven patients treated with the drug over a sustained period. An impression of clinical improvement was gained in one patient, but there was no associated reduction in plasma hGH concentrations. It seems likely that acromegalic patients who have failed to respond to conventional treatment may be more resistant to bromocriptine therapy.     

重组人生长激素治疗生长激素缺乏性侏儒症

20例原发性垂体性侏儒症、2例单纯性GH缺乏IA型及1例宫内生长停滞的患儿用经典性药物进行激发试验并于夜睡眠中采血测GH,确认有GH缺乏。全部病例用重组hGH治疗。20例用191肽的Genotropin,3例用192肽的Somatonorm,疗程12个月(后一组中1例治疗6个月)。结果一年后身高增长Genotropin组为13.3±1.8cm,Somatonorm组2例各为16.0、16.6cm,1例治疗6个月后为7.9cm。疗程中出现血清T_4下降、轻度肝肿大、一过性血尿者各占47.8％、30.4％、30.4％。     

尿hGH测定在肢端肥大症诊断中的价值

应用尿hGH免疫放射测定法,测定了12例成年男性、12例成年女性和17例肢端肥大症夜10小时尿hGH排泄量,分别为0.58±0.56ng,0.52~0.37ng和167.1±278.2ng。肢端肥大症夜10小时尿hGH排泄量显著高于正常人(P<<0.001),且无一例重叠。通过8例肢端肥大症上午8小时血清hGH谱与夜10小时尿hGH排泄量的观察,发现两者呈显著相关,提示夜晚和日间可能有相同的hGH分泌模式,尿hGH排泄量测定能够反映血清hGH分泌情况。提示,用本法测定尿hGH排泄量有助于诊断肢端肥大症。     

重组人生长激素治疗对生长激素缺乏症患者甲状腺功能的影响

为探讨生长激素治疗对甲状腺功能的影响及其机制，给１９例特发性生长激素缺乏症患者每日皮下注射重组人生长激素（ｒｈＧＨ）Ｇｅｎｏｔｒｏｐｉｎ０．１ＩＵ／ｋｇ体重，治疗１年，观察治疗前后甲状腺功能及血促甲状腺激素（ＴＳＨ）对静脉推注促甲状腺素释放激素（ＴＲＨ）的反应。经Ｇｅｎｏｔｒｏｐｉｎ治疗后，患者血清Ｔ４及ＦＴ４水平较治疗前明显下降（Ｐ＜０．０１）；治疗半年后，血清ＦＴ３水平亦较治疗前下降（Ｐ＜０．０５）；而血清Ｔ３、３，３′，５′－三碘甲状腺原氨酸及ＴＳＨ水平无明显变化（０．２＜Ｐ＜０．３）。治疗１年后，８例患者血清ＦＴ４水平降至正常范围以下，依此将患者分为治疗后甲状腺功能正常组及降低组，结果证实甲状腺功能降低组在治疗前或治疗后ＴＳＨ对ＴＲＨ兴奋的反应均较甲状腺功能正常组高（Ｐ＜０．０５）。血清ＴＳＨ对ＴＲＨ的反应增强提示患者治疗前就已有潜在的ＴＲＨ缺乏，后者可能是ｒｈＧＨ治疗过程中ＦＴ４及Ｔ４水平下降的潜在基础。因此在ｒｈＧＨ治疗过程中需监测特发性生长激素缺乏症患者的甲状腺功能，以及时给予替代治疗。     

EVALUATION OF THE RESULTS OF TRANS-SPHENOIDAL SURGERY IN ACROMEGALY BY ASSESSMENT OF THE GROWTH HORMONE RESPONSE TO THYROTROPHIN-RELEASING HORMONE

Eighteen acromegalic patients GH-responsive to TRH were reinvestigated following trans-sphenoidal surgery and radiotherapy. Basal serum GH decreased below 10 microgram/1 in thirteen cases; nine of them became GH-unresponsive to TRH 1 month after operation, and another one following conventional pituitary irradiation. Four of these ten patients also showed a normal GH response to L-Dopa after treatment, and five responded normally to insulin-induced hypoglycaemia; two patients had a normal GH secretory pattern after both these stimuli. No recurrences were observed over a follow-up period of 15-80 months among the ten patients who became GH-unresponsive to TRH following operation, while one of the three subjects still responsive to TRH in spite of normalized basal serum GH concentration relapsed 10 months after surgery. Three patients with normalized TRH test following operation were repeatedly reinvestigated over a 3-6 years period and always found unresponsive. The present study shows that the 'paradoxical' GH responses to TRH and L-Dopa frequently disappear after surgery, that complete normalization of GH secretory pattern may rarely be attained, and that the disappearance of GH response to TRH probably indicates satisfactory treatment of acromegaly. These data suggest that the 'paradoxical' GH responses frequently found in acromegaly are dependent on the adenoma per se and not on hypothalamic dysfunction.     

THYROTROPHIN RELEASING HORMONE INDUCED CALCITONIN SECRETION IN PATIENTS WITH MEDULLARY CARCINOMA OF THE THYROID

An i.v. bolus injection of 500 μg TRH caused a prompt increase in plasma calcitonin (CT) in two patients with medullary thyroid carcinoma (MTC). In case 1 with a sporadic MTC, plasma CT increased from 0.32 ng/ml to 0.70 ng/ml 2 min after TRH. In the second case with multiple endocrine neoplasia (MEN) type II, plasma CT increased from 0.39 ng/ml to 4.7 ng/ml 2 min after the injection. None of five normal healthy subjects and a patient with thyroid follicular adenocarcinoma had significant changes in plasma CT levels after TRH. Studies with monolayer cultures of MTC cells derived from one patient revealed that TRH stimulated CT release. Incubation of the cells with TRH of 10⁻⁶ m or 10⁻⁵ m for 1 h increased CT concentration in the medium to 140% or 182% of the control level, respectively. Under the same conditions, pentagastin (10⁻⁶ m ) increased CT concentration in the medium to 156%. These results indicate the direct stimulatory effect of TRH on CT secretion in the patients with MTC.     

THE EFFECT OF OESTROGENS ON HUMAN CALCITONIN SECRETION AFTER CALCIUM INFUSION IN ELDERLY FEMALE SUBJECTS

The effect of oestrogen administration (4–6 weeks) on the response of human calcitonin (hCT) secretion to 5 min calcium infusions was studied in ten elderly women. There was no significant difference in mean basal plasma hCT levels before and after oestrogen administration. However, the mean increment in plasma hCT in response to calcium infusion (ΔhCT) increased significantly (P < 0·001) from 21·9±6·6 (mean ±SE) before treatment, to 79·6±15·5 ng/l after oestrogen administration. Mean serum calcium levels decreased significantly (P < 0·001) from 2·42 ±0·06 before to 2·19·0±07 mmol/l after oestrogen treatment. Mean plasma immunoreactive PTH (iPTH) levels increased significantly (P < 0·05) from 521·41 before to 696·96 ng/l after oestrogen treatment. To exclude out the possibility that the decreased serum calcium level itself might have influenced ΔhCT, 1α-hydroxycholecalciferol (1α-OH-D₃) was administered with oestrogens. While this resulted in a slight increase in serum calcium level, there was no significant difference in ΔhCT in response to calcium infusion following oestrogen treatment alone, and after combination therapy of oestrogen and 1 α-OH-D₃. The primary action of administered oestrogen may be in stimulating hCT secretion which results in a decrease in plasma calcium concentration and an increase in plasma iPTH level.     

A COMPARISON OF THE EFFECT OF LEVODOPA AND SOMATOSTATIN ON THE PLASMA LEVELS OF GROWTH HORMONE, INSULIN, GLUCAGON AND PROLACTIN IN ACROMEGALY

The acute suppressive effects of L-dopa and somatostatin (growth hormone release inhibiting hormone) on the elevated plasma GH concentrations of seven patients with acromegaly were compared. In addition the effects of the two agents on fasting concentrations of plasma glucose, insulin, glucagon and prolactin were studied. In six of the seven patients hourly samples for GH assay were taken from 08.00 to 20.00 hours on a control day. Synthetic cyclic somatostatin (100 mug) was infused intravenously in an albumin/saline solution over 75 min with a Harvard constant infusion pump. Levodopa 500 mg was given orally. Somatostatin infusion produced a reduction in plasma GH concentrations in six of seven patients (mean reduction 55%). L-Dopa produced a reduction in plasma GH concentrations in the same six patients (mean reduction 52%). The minimum GH concentrations achieved in the two tests were comparable and did not differ significantly from the minimum GH concentrations recorded during the 12 h control study. Mean plasma insulin and glucagon concentrations were also significantly reduced during the somatostatin infusion (P less than 0-025; P less than 0-05 respectively). Plasma glucose concentrations did not change. L-Dopa did not alter mean plasma glucose, insulin or glucagon values. Somatostatin did not alter prolactin values but L-Dopa suppressed basal values to less than 2 ng/ml in five patients. This study shows that the plasma GH change after the administration of L-dopa and somatostatin in acromegaly is comparable and confirms the pancreatic effects of somatostatin.