The efficacy and safety of long-term Norditropin® treatment in children with Prader-Willi syndrome

Prader-Willi syndrome is a genetic disorder that is associated with short stature, partial growth hormone deficiency, small hands and feet, learning and behavioural problems, and hyperphagia leading to severe, often morbid, obesity. Growth hormone therapy is associated with an improvement in height and body composition. We evaluated the efficacy and safety of long-term growth hormone treatment in a retrospective observational multinational study of 41 prepubertal children (mean age 3.8±3.0 years) with genetically diagnosed Prader-Willi syndrome treated with growth hormone (0.03-0.06 mg/kg/day) for >12 months [mean duration 4.1 (range 0.9-9.5) years]. Height, weight, and body composition measurements were recorded at baseline and at 6 month intervals until last observation. Mean (SD) gain in height at 12 months was 0.9 (0.2) SD score (p<0.0001). At last observation (after approximately 6 years) mean gain in height was 1.3 (0.3) (p=0.0001) with 85% of children achieving height>- 2 SD score. Body composition improved during treatment with an estimated 9.1% increase in lean body mass and 9.1% decrease in fat mass at last observation (p=0.019). Scoliosis was reported in 3 patients at baseline and 8 patients at last observation. Sleep apnoea was recorded in 3 (7.3%) patients. There were no other severe adverse events reported. Long-term growth hormone treatment of prepubertal children with Prader-Willi syndrome was associated with significant improvements in height and body composition. Treatment was well tolerated. The development of scoliosis warrants monitoring by an orthopaedic specialist.

Growth hormone effects on cortical bone dimensions in young adults with childhood-onset growth hormone deficiency

Growth hormone (GH) treatment in young adults with childhood-onset GH deficiency has beneficial effects on bone mass. The present study shows that cortical bone dimensions also benefit from GH treatment, with endosteal expansion and increased cortical thickness leading to improved bone strength.

INTRODUCTION

In young adults with childhood-onset growth hormone deficiency (CO GHD), GH treatment after final height is reached has been shown to have beneficial effects on spine and hip bone mineral density. The objective of the study was to evaluate the influence of GH on cortical bone dimensions.

METHODS

Patients (n = 160; mean age, 21.2 years; 63% males) with CO GHD were randomised 2:1 to GH or no treatment for 24 months. Cortical bone dimensions were evaluated by digital x-ray radiogrammetry of the metacarpal bones every 6 months.

RESULTS

After 24 months, cortical thickness was increased compared with the controls (6.43%, CI 3.34 to 9.61%; p = 0.0001) and metacarpal index (MCI) (6.14%, CI 3.95 to 8.38%; p < 0.0001), while the endosteal diameter decreased (-4.64%, CI -7.15 to -2.05; p < 0.001). Total bone width did not change significantly (0.68%, CI -1.17 to 2.57%; not significant (NS)). A gender effect was seen on bone width (p < 0.0001), endosteal diameter (p < 0.01) and cortical thickness (p < 0.01), but not with MCI (NS).

CONCLUSIONS

Cortical bone reacts promptly to reinstitution of GH beyond the attainment of final height by increasing the cortical thickness through endosteal bone growth. This leads to a higher peak bone mass and may reduce the risk of cortical bone fragility later in life.

A follow-up study of hypertensive patients after operative treatment of unilateral renovascular or renal disease

A study of 44 hypertensive patients with unilateral renovascular or renal parenchymal disease is presented. All patients underwent corrective surgery. Out of the 44 operated patients, five did not participate in the follow-up examination. The remaining 39 patients constitute the study population. The effects of surgery on the hypertensive state could be evaluated in 35 patients, whereas four died less than two months after the operation. Follow-up studies were carried out at 8-60 months after the operation. The average period of observation was 32 months; 24 patients were observed for more than two years. As a group, the patients had severe hypertension with extensive target organ damage and widespread atherosclerosis. A fairly rigorous selection process was applied, and an unsatisfactory response to medical management was considered a point of major importance. In the majority of cases, renovascular lesions were atherosclerotic, with only two cases of fibromuscular dysplasia. Unilateral nephrectomy was performed in 32 patients, whereas seven underwent reconstructive vascular surgery. Out of 35 patients, 22 (63%) were cured, 8 (23%) improved and 5 (14%) unaltered. A gratifying regression of hypertensive lesions in target organs was observed in patients who were cured or improved by surgery. The frequency and severity of postoperative complications were related to the presence of extrarenal vascular disease.

Long-term effects of continuous subcutaneous infusion versus daily subcutaneous injections of growth hormone (GH) on the insulin-like growth factor system, insulin sensitivity, body composition, and bone and lipoprotein metabolism in GH-deficient adults

It remains uncertain whether close imitation of the physiological pulsatile GH pattern determines the effects of GH treatment in humans. However, human studies have reported comparable metabolic responses to short-term constant and intermittent GH exposure. The aim of the study was to compare the metabolic effects of GH after continuous and intermittent sc delivery. In a parallel design, 14 GH-treated GH-deficient patients (mean age, 37 yr; mean body mass index, 27.4 kg/m(2)) were studied during steady state at the start of the study and after 6 months. Seven patients received daily injections (inj) in the evening as usual, and 7 received a continuous infusion (inf) of GH by means of a portable pump. The GH dose was kept unchanged before and during the study. Serum levels of insulin-like growth factor I (IGF-I) tended to increase in the patients switched to constant infusion (from 175 +/- 36 to 209 +/- 50 microg/L), but the differences obtained during the two regimens [+34.3 (inf) vs. -11.9 (inj)] were not significant (P = 0.34). Serum levels of IGF-II (P = 0.71) and IGF-binding protein (IGFBP)-3 (P = 0.75) were identical during the two modes of treatment. Serum levels of IGFBP-1 (P = 0.72), IGFBP-2 (P = 0.34), and GH-binding protein (P = 0.75) were unaffected by treatment regimen. Serum levels of free fatty acids, reflecting lipolysis, decreased significantly (16%) in the group switched to GH infusion (difference, -99.8 vs. +5 micromol/L; P < 0.03). The GH pattern did not influence insulin sensitivity (P = 0.71) or glucose effectiveness (P = 0.15) derived from Bergman's minimal model. Similarly, the two treatment regimens had no differential impact on lipoprotein levels, bone metabolism, or body composition. In conclusion, continuous and intermittent administrations of GH for 6 months are comparable with respect to the IGF-IGFBP axis, whereas intermittent exposure may be of importance for the lipolytic effect of GH. The data on insulin sensitivity and lipoproteins suggest that constant GH exposure is as safe as intermittent GH administration.

Characterization of growth hormone-releasing hormone stimulation of the endocrine pancreas: studies with alpha- and beta-adrenergic and cholinergic antagonists

The 40 aminoacids residue of pancreatic growth hormone-releasing hormone stimulates the secretion of insulin, glucagon, an somatostatin from the pancreas. To determine whether this stimulation of islet hormone secretion is mediated via adrenergic or cholinergic receptor sites, we studied the effects of 30 nmol/l of the growth hormone-releasing hormone on the release of insulin, glucagon, and somatostatin in the presence of either alpha-adrenergic (phentolamine), beta-adrenergic (propranolol) or cholinergic (atropine) blocking agents. The responses to the growth hormone-releasing hormone were not significantly modified by adrenergic or cholinergic blockers. The findings rule out an interaction with adrenergic and cholinergic receptors on islet cells. It is at present unknown whether the growth hormone-releasing hormone stimulates islet hormone secretion via an interaction with specific growth hormone-releasing hormone receptors or vasoactive intestinal peptide receptors.

Synthetic pancreatic growth hormone-releasing factor (GRF-40) stimulates the secretion of the endocrine pancreas

The effects on islet hormone secretion of the synthetic replicates of two peptides with potent GH-releasing activity isolated from human pancreatic islet cell tumors (GRF-40 and GRF-44) were studied using the isolated, perfused dog pancreas. GRF-40 produced a dose-dependent stimulation of insulin, glucagon, and somatostatin secretion. The responses to GRF-40 were modified by the prevailing glucose level: higher insulin and somatostatin and lower glucagon responses were obtained at high rather than low glucose. In contrast, GRF-44 did not produce any stimulation of the endocrine pancreas. In vivo GRF-40 and GRF-44 elicited identical pronounced growth hormone responses in the rat. The findings reported here provide support that pancreatic insulin and glucagon are modulated by GRF-40 with somatostatin as its inhibitory counterpart. The question, whether GRF-40 is of physiologic relevance in the regulation of the endocrine pancreas, must await evidence that it is present and releasable from the pancreas.

Double-antibody solid-phase radioimmunoassay for blood bradykinin

A solid phase radioimmunoassay for the determination of blood bradykinin has been developed. Highly specific antibodies against bradykinin were raised in rabbits after coupling the peptide to thyroglobulin. Iodination of [Tyr8]-bradykinin was carried out with a chloramine-T procedure resulting in a tracer with high specific activity. Bradykinin was isolated in the following way: blood was sampled directly into acetone, and lipids were removed by extraction with petroleum either (40-60 degrees C). The final purification was made on QAE-Sephadex A-25 at pH 7.4. The mean recovery of added [125I-Tyr8]-bradykinin was 28% with a sample volume of 6 ml whole blood. The sensitivity of the radioimmunoassay was 1.25 pg/tube or 3 pg/ml blood. The reproducibility of the method is satisfactory with a between-assay coefficient of variation below 16%. Levels found in venous blood were below 3 pg bradykinin/ml in normal persons.

Solid-phase double-antibody radioimmunoassay of pepsinogen I in serum

A solid-phase radioimmunoassay for the determination of pepsinogen I in serum has been developed. The antibody was raised in rabbits with pepsinogen I isolated from urine as previously described. Radioiodination was carried out with a chloramine-T procedure resulting in a tracer with excellent shelf life. In the standard procedure with a 24-h incubation time, followed by 2-h incubation with a second antibody coupled to a solid phase, 50 microliter serum was analyzed, standard range 1.88-60 ng PG I. An eight times more sensitive method was also developed using sequential saturation techniques. Specificity studies demonstrated 0.6% crossreactivity with PG II. The immunoreactivity of PG I purified from urine was nearly identical with the immunoreactivity of PG I purified from gastric mucosa. The levels of PG I in serum from 121 control subjects were similar to those obtained with conventional phase separation methods. It is concluded that the method is simple, precise and free from non-specific serum interference.

Rate of angiotensin II generation within the human pulmonary vascular bed

Plasma angiotensin II concentration gradients across the pulmonary vascular bed were measured during diagnostic renal venous/right heart catheterization in twenty-seven hypertensive patients with renal or renovascular disease. There was a linear correlation between the plasma angiotensin II concentration in mixed venous blood and in systemic arterial blood. The pulmonary angiotensin II production rate was measured in fourteen patients. This parameter was linearly correlated with plasma renin concentration in systemic arterial blood. The plasma clearance of angiotensin II across the systemic vascular bed varied from 0.7 to 1.71/min, i.e. within a fairly narrow range.

Plasma noradrenaline concentration in hypertensive and normotensive forty-year-old individuals: relationship to plasma renin concentration

Forty-year-old individuals with labile and with mild sustained essential hypertension, identified during a survey of a population born in 1936, were investigated. None had ever received antihypertensive treatment. In thirty-three individuals (26 M, 7F) with diastolic blood pressure (DBP) greater than or equal to 95 mmHg at the very first examination and in thirty-one (14 M, 17 F) randomly selected normotensive controls plasma noradrenaline concentration (PNAC) was measured at rest supine. In twenty-two patients (16 M, 6 F), with sustained diastolic hypertension (diastolic blood pressure greater than or equal to 95 mmHg on at least three different occasions) and in twenty-four (14 M, 10 F) normotensive controls PNAC and plasma renin concentration (PRC) were measured supine at rest and again 2 h after furosemide and ambulation. Basal and acutely stimulated values for PNAC and PRC were identical in hypertensive and normotensive individuals. A close correlation between PNAC and PRC after acute stimulation (r = 0.77, P < 0.001) as well as between the absolute changes from resting to acutely stimulated values (r = 0.72, P < 0.001) were found in the hypertensive individuals. It is concluded that sympathetic nerve activity, as defined from measurements of plasma noradrenaline concentration, is similar in young patients with mild hypertension and in normotensive controls. We propose that the discrepancies found in the literature might be related to a lack of comparability between hypertensive and normotensive individuals studied, as far as the source of study populations is concerned.

The use of an angiotensin II antagonist (saralasin) as an adjunct during renal vein catheterization

Renal vein catheterization was performed in fifteen hypertensive patients with unilateral renal disease. Samples for measurement of plasma renin concentration were obtained from each of the two renal veins and from the femoral artery (or the inferior caval vein)-before and during saralasin infusion. Saralasin infusion induced a significant decrease in blood pressure. In ten patients with lateralization of renin secretion before infusion, saralasin induced a 2-fold increase of the renin gradient across the diseased kidney, whereas there was no significant renin gradient across the contralateral kidney neither before nor after saralasin infusion. Thus, the renal venous renin ratio (diseased/contralateral) increased from a mean value of 2.10 to 4.13. In five patients without lateralization of renin secretion prior to infusion, saralasin induced a significant increase of renin gradient across both kidneys. In consequence, evidence for lateralization did not emerge and the renal vein renin ratio remained unchanged at 1.10. In cases with lateralization of renin secretion, the use of saralasin provides confirmatory evidence for strictly unilateral renin secretion with suppression of renin output from the contralateral kidney. In patients without obvious lateralization of renin secretion before saralasin, the administration of this angiotensin II inhibitor can serve to demonstrate a potential renin for renin secretion, shared by both kidneys.

Plasma noradrenaline concentration in hypertensive and normotensive 40-year-old individuals: relationship to plasma renin concentration

1. Forty-year-old individuals with mild essential hypertension, identified during a survey of a population born in 1936, were investigated. Forty-year-old normotensive subjects, drawn from the same population, served as a control group. 2. Plasma noradrenaline concentration and plasma renin concentration at rest supine and after acute stimulation, as induced by frusemide intravenously and ambulation, did not differ from reference values in the 40-year-old normotensive controls. In the hypertensive group a close correlation (r = 0.77, P less than 0.001) was found between plasma noradrenaline and plasma renin concentration after acute stimulation. 3. Sympathetic nerve activity, as defined by measurements of plasma noradrenaline, is normal in mild essential hypertension. Discrepancies described in the literature are probably related to a lack of comparability between hypertensive and normotensive study populations.

Renin--angiotensin system in mild essential hypertension. The functional significance of angiotensin II in untreated and thiazide-treated hypertensive patients

1. Twenty-five patients with mild essential hypertension, identified during a survey of a population born in 1936, were investigated.

2. Basal and post-frusemide values for plasma renin concentration and plasma angiotensin II concentration did not differ markedly from reference values in 25 40-year-old control subjects. In the untreated, sodium replete state saralasin infusion (5·4 nmol min−1 kg−1) produced an increase in mean arterial pressure in the patient group as a whole.

3. Twenty-one patients were treated with hydrochlorothiazide, mean dose 75 mg/day for 3 months. Pre-treatment, frusemide-stimulated plasma renin concentration and plasma angiotensin II, and values during thiazide treatment were higher in ‘non-responders’ (n = 10) to hydrochlorothiazide treatment than in ‘thiazide-responders’ (n = 11). During thiazide therapy, angiotensin II blockade induced a clear-cut decrease in mean arterial pressure in all ‘thiazide-nonresponders’ whereas only four out of 11 ‘thiazide-responders’ showed a borderline decline in mean arterial pressure.

4. The functional significance of the renin—angiotensin system in mild essential hypertension emerges only after thiazide treatment. Thiazide-induced stimulation of the renin—angiotensin system counter-balanced the hypotensive effect of thiazide in some 40% of the treated patients. Thus the responsiveness of the renin—angiotensin system determined the blood pressure response to thiazide treatment.

Different secretion patterns of active and inactive renin in man

1. In plasma samples from normal subjects and patients with untreated essential hypertension, the concentration of inactive renin (as measured after acidification) was on average 4-5 times higher than the concentration of active renin (as measured without acidification).2. Plasma angiotensin II concentration was correlated to active renin but not to inactive renin. 3. A hyperacute stimulation induced by infusion of saralasin resulted in a marked rise of active renin, whereas inactive renin remained unchanged. 4. An acute stimulation induced by frusemide and ambulation led to a considerable rise in active renin and a slight, but significant, rise of inactive renin. 5. Stimulation with oral thiazide over 5 days induced a seven-fold rise of active renin, with a doubling of inactive renin. Thiazide treatment for 3 months led to a four-fold rise of active renin and a three-fold rise of inactive renin. 6. There was no difference between the concentrations of inactive renin in systemic plasma, ipsilateral and contralateral renal venous plasma in 12 patients with renovascular hypertension, neither before nor after infusion of saralasin with the associated fall in blood pressure. 7. We conclude that the time constants pertinent to secretion or release of active and inactive renin in man are of different orders of magnitude.

Pseudohypoaldosteronism. Clinical, biochemical and morphological studies in a long-term follow-up

A boy with pseudohypoaldosteronism was followed from birth to the age of 7 years. Failure to thrive, vomiting, dehydration, hyponatraemia and urinary sodium loss were prominent findings. Urinary excretion of corticosteroid metabolites was normal. Before treatment, excessively high plasma renin concentration was found, associated with a marked activation of aldosterone secretion. A renal biopsy showed pronounced hypertrophy of the juxtaglomerular apparatus. Persisting metabolic acidosis and an insufficient urinary acidifying capacity suggested the presence of distal renal tubular acidosis. Treatment with sodium bicarbonate and sodium chloride from 19 to 31 months of age resulted in normal growth and normal physical and mental development. The plasma electrolytes were normalized but a pronounced activation of the renin-aldosterone system persisted after therapy, and on sodium restriction this system responded with a considerable further activation.

Partial purification of human renin substrate

A two-step purification method is described for the preparation of renin substrate from human plasma. Pooled plasma from women on oral contraceptives is used for the purification. The overall yield of renin substrate is 57%, with a twenty-fold purification. The specific renin substrate content of the preparation, as determined by enzymatic degradation with an excess of human renin, is 2 mug angiotensin I per mg protein. The product has a very low endogenous renin activity and is free from angiotensinase activity. An additional purification step involving affinity chromatography is described. In pilot studies a renin substrate yield of 37% has been achieved, with a hundred-fold purification. The final product has a specific renin substrate content of 10 mug angiotensin I per mg protein. The preparation contains up to 12 different plasma proteins, nine of which have been identified and quantitated.

Measurement of angiotensin II in human plasma: technical modifications and practical experience

This paper presents our experience in measurement of plasma angiotensin II concentration according to the method described by Düsterdieck, G. and McElwee, G. (1971) Eur. J. Clin. Invest. 2, 32-38. Certain technical modifications of the procedure have been worked out. For each individual plasma sample, the recovery across extraction and elution steps is determined by addition of radio-iodinated angiotensin II. A time-saving recycling elution procedure is described. Evidence for the clinical applicability of the modified method is presented.