Urinary human growth hormone measurement using a highly sensitive sandwich enzyme immunoassay: diagnostic and therapeutic uses in patients with growth hormone deficiency

Several reports indicate that urinary hGH excretion is significantly lower in patients with either partial (PGHD) or complete GH deficiency (CGHD) than in normal but short children (NSC) or normal children (NC). However, there is an overlap between the NSC and NC groups and the PGHD group. Using a highly sensitive sandwich enzyme immunoassay, we investigated whether the measurement of urinary hGH can clearly separate the PGHD and CGHD groups from the NSC and NC groups. In addition, we measured the urinary excretion of synthetic methionyl-hGH (met-hGH) in PGHD and CGHD after sc injections of 2 and 4 IU and im injections of 4 IU in an attempt to determine the optimal replacement dose. Total 24-h urinary hGH excretion in each patient examined for 2 consecutive days varied from 1 day to the next. There were no differences in urinary hGH excretions between the NSC group and the NC group. The lower values for daily urinary hGH excretion in the NSC group overlapped some of the higher values in the PGHD group. However, when the mean urinary hGH level of both days was used, the 24-h urinary hGH excretion clearly separated the PGHD (5.5 +/- 2.3 ng/day; range, 1.3-9.2; n = 21) and CGHD (1.9 +/- 0.9 ng/day; range, 0.6-3.6; n = 14) groups from the NSC (12.8 +/- 3.1 ng/day; range, 9.3-17.5; n = 10) and NC (14.6 +/- 3.1 ng/day; range, 10.6-19.0; n = 6) groups without any overlap. A mean urinary hGH value less than 9.0 ng/day during a 2-day collection strongly suggested GH deficiency. Ten of 16 patients with PGHD and CGHD who received 2 IU met-hGH, sc, had urinary hGH levels within the range of the mean +/- SD in NSC. These patients received daily sc 0.097 +/- 0.024 IU/kg hGH injections. These results suggest that the measurement of 24-h urinary hGH excretion is noninvasive, accurate, and useful for the screening of GH deficiency. The mean value on 2 days of 24-h urinary hGH excretion for the screening of GH deficiency is estimated to be less than 9.0 ng/day. The optimal dose of GH as therapy for GH deficiency is demonstrated as daily sc injection of 0.1 IU/kg hGH, 0.7 IU/kg/week. To convert international units of met-hGH to milligrams, divide by 2.4.     

Growth hormone (GH) pharmacogenetics: influence of GH receptor exon 3 retention or deletion on first-year growth response and final height in patients with severe GH deficiency

CONTEXT: A polymorphism in GHR gene, the presence or absence of exon 3, has been shown to influence the 1- and 2-yr growth responses to human recombinant GH (hGH) therapy in children without GH deficiency (GHD). OBJECTIVE: The objective of this study was to assess the influence of GHR-exon-3 genotype on the short and long-term response to hGH therapy in children with GHD. SETTING: The study was conducted in the university hospital. DESIGN AND PATIENTS: Genotype and retrospective analysis was performed on data of 75 children with GHD. Intervention: Intervention consisted of hGH treatment at a mean dose of 33 mug/kg.d and GHR-exon-3 genotype by multiplex PCR. MAIN OUTCOME MEASURES: The main outcome measures were GHR genotype: full-length (fl) and exon 3-deleted (d3) alleles, growth velocity in 58 children who remained prepubertal during the first year, and adult height in 44 patients with GHD after 7.5 +/- 3.0 yr of treatment. RESULTS: Clinical and laboratory data at the start of treatment and hGH doses were indistinguishable among patients with different GHR-exon-3 genotypes (fl/fl vs. fl/d3 or d3/d3). Patients carrying at least one GHRd3 allele had a significantly better growth velocity in the first year of hGH replacement (12.3 +/- 2.6 vs. 10.6 +/- 2.3 cm/yr; P < 0.05) and achieved a taller adult height (final height sd score, -0.8 +/- 1.1 vs. -1.7 +/- 1.2; P < 0.05) when compared with patients homozygous for GHRfl alleles. CONCLUSIONS: Patients with GHD who are homozygous for GHR exon 3 fl were less responsive to short- and long-term hGH therapy. Approximately half of the population is homozygous for GHRfl, and future studies adjusting hGH therapy to genotype may improve outcome.     

The effect of hGH deficiency on the insulin response to glucagon after oral glucose loading

Summary Six children and adolescents (aged from 2 6/12 to 16 years) with isolated hGH deficiency were subjected to a standard oral glucose tolerance test (OGTT) followed by the administration of IV glucagon at 180 mins. Three of them underwent a second test after several months of hGH therapy. Nine patients underwent a separate IV glucagon test and two of these patients had both tests. As controls served 14 endocrinologically normal children and adolescents, who underwent both tests. It was found that the patients with isolated hGH deficiency had lower basal plasma insulin and blood glucose levels and that their insulin response to IV glucagon even after oral glucose preloading was significantly lower than in the control group. This response was partially restored by several months of hGH treatment in the three patients tested. These findings are interpreted as further evidence for an insulinotrophic effect of hGH.Established Investigator of the Chief Scientist's Bureau, Ministry of Health     

Evidence of a growth hormone-releasing hormone-like molecule in salmon brain, Oncorhynchus keta and O. kisutch

An antiserum with conformational specificity to human growth hormone-releasing hormone (hGH-RH 1-44 NH2) was produced and used to develop a radioimmunoassay to detect immunoreactive (ir) GH-RH in brain extracts of salmon, guinea pig, and mouse. Evidence of an immunoreactive GH-RH from salmon brain extracts with a retention time on reverse-phase high-performance liquid chromatography (HPLC) distinct from hGH-RH 1-44 is presented. Salmon irGH-RH from crude extracts elutes 1-2 min earlier than hGH-RH 1-44 (NH2) in a gradient HPLC system, whereas affinity-purified salmon irGH-RH elutes 12-13 min earlier in a near-isocratic system, suggesting that the salmon molecule is more hydrophilic.     

Normal growth hormone secretion in growth hormone insufficient children retested after completion of linear growth

OBJECTIVE The recognition of the syndrome of adult GH deficiency suggests that young GH deficient adults, deprived of GH replacement at completion of linear growth, may suffer effects of GH deficiency. We assessed GH reserve in young adults previously diagnosed as having idiopathic GH insufficiency, who were treated with hGH replacement (14 IU/m²/week) in childhood. DESIGN Eight patients (7 males, 1 female) diagnosed as having GH insufficiency by insulin tolerance test (ITT) in childhood (ages 8.5–15.6 years) were retested by ITT at completion of linear growth (ages 15.1–19.6 years), 3 months after discontinuation of hGH therapy. MEASUREMENTS GH reserve was measured during ITT at diagnosis and at retesting. Height velocity (HV) and HV SDS were calculated before and during GH therapy. RESULTS At diagnosis, the mean peak GH response to ITT was 10.5 ± 2.0 mU/l (range 7.7–13.6). At retesting, mean GH was 52.4 ± 33.2 mU/l (range 10.4–100), 7/8 subjects having peak GH levels greater than 15 mU/l. During hGH therapy mean HV increased from 4.0 ± 1.5 cm/year at diagnosis to 7.3 ± 1.9 cm/year during the 1st year (P = 0.004) and 6.9 ± 2.3 cm/year during the 2nd year (P = 0.02). Mean HVSDS increased from ?1.6 ± 2.1 at diagnosis to 3.1 ± 2.9 during the 1st year (P = 0.004) and 2.2 ± 4.2 during the 2nd year (P = 0.05, NS) of treatment. CONCLUSIONS Seven out of 8 children diagnosed as having idiopathic GH insufficiency had normal GH secretion at completion of linear growth. Children with GH insufficiency cannot be assumed to become GH deficient adults and should not continue on GH therapy into adult life without reinvestigation. All who were GH insufficient children should be retested at completion of linear growth to identify those who are truly GH insufficient adults and may benefit from replacement therapy.     

Negative correlation between peripheral plasma somatostatin levels and GH responses to GH-RH stimulation tests in children

On forty-six fasting and resting children, aged 5-17 years, with short stature (below -2 SD) a growth hormone releasing hormone (GH-RH) stimulation test (2 micrograms/kg iv bolus, Sanofi) was performed. Twenty-two children were prepubertal, of which, 13 had a constitutional short stature (CSS), nine an idiopathic growth hormone deficiency (IGHD). Twenty-four subjects were pubertal, at the stage II or III of Tanner. Among them, six had a constitutional short stature (CSS) and 18 an idiopathic delayed puberty (IDP). Blood samples were taken for determination of plasma somatostatin-like immunoreactivity (SLI) in chilled test tubes containing EDTA + aprotinin. Plasma SLI levels were measured after extraction and concentration on C18 Sep Pack columns by radioimmunoassay using an antibody against 1-14 somatostatin. The sensitivity of this assay is around 3 pg/ml. After GH-RH stimulation the peak of GH (mean +/- SEM) was in prepubertal subjects: 25.3 +/- 9.1 micrograms/l in CSS, and 18.6 +/- 10.3 micrograms/l in IGHD. In pubertal subjects GH peaks were 17.6 +/- 8.4 micrograms/l in CSS and 15.6 +/- 3.8 micrograms/l in children with IDP. No significant differences was found between basal plasma SLI levels in the four groups of subjects, being respectively (mean +/- SEM) 11.9 +/- 1.8 pg/ml in prepubertal subjects with CSS, 9.6 +/- 2.6 pg/ml in IGHD, 7.6 +/- 1.7 pg/ml in pubertal children with CSS and 6.6 +/- 1.5 pg/ml in children with IDP.(ABSTRACT TRUNCATED AT 250 WORDS)     

Reversible hypothyroidism in growth hormone-deficient children treated with human growth hormone.

Six children with human growth hormone (hGH) deficiency became hypothyroid during the course of their therapy with hGH. This was accompanied by a decreasing growth rate, clinical symptoms of hypothyroidism and decreased serum T4 concentrations. Three of the 6 patients returned to the euthyroid state, both clinically and biochemically, with cessation of hGH therapy, and reinstitution of hGH precipitated hypothyroidism again in 2 of the three. The patients who remained hypothyroid have evidence of multiple pituitary trophic hormone deficiencies while those who reverted to euthyroidism appear to have isolated hGH deficiency. Evaluation of thyroid function while on hGH showed low T4, free T4 and T3 concentrations. The serum thyrotropin (TSH) response to thyrotropin-releasing hormone (TRH) was absent or markedly blunted in 4 of 6 patients while receiving long-term hGH therapy but was normal or exaggerated in all patients when tested before or after only 5 days of hGH therapy. These data indicate that exogenous hGH results in an inhibition of the TSH response to TRH. The mechanism of this inhibition is unclear, but we postulate that it may be mediated by somatostatin secretion in response to pulse doses of hGH.     

A recombinant-DNA-derived modification of human growth hormone (hGH44-191) with enhanced diabetogenic activity

A modified human growth hormone (hGH) that lacks the first 43 residues of the intact hormone was prepared by recombinant-DNA technology. For preparative purposes an additional alanine was made the amino terminal residue. Sequence analysis and tryptic peptide mapping combined with amino acid analyses confirmed the structure of the polypeptide. Less than 2% N-terminal methionine was detected. The hGH44-191 was estimated to be at least 10 times more active than hGH in producing glucose intolerance in obese yellow mice (Avy/A) and was equipotent to hGH in increasing serum free fatty acids in fasted, hypophysectomized rats. The peptide did not promote growth in hypophysectomized rats nor did it exhibit early (1h) insulin-like activity in fasted, hypophysectomized rats, as indicated by its failure to lower blood glucose and fatty acids. The modified hGH was inactive in the Nb-2 cell assay but was about one-third as active as hGH in stimulating the pigeon crop sac. In radioimmunoassays using 125I-labeled hGH and polyclonal antibodies to intact hGH, cross-reactivity of hGH44-191 was less than 1%. We conclude that removal of the amino terminal portion of hGH enhances its diabetogenic properties, and that this activity does not depend upon the ability to promote growth. Furthermore, the insulin-like activity can be separated from its diabetogenic action by deletion of the first 43 amino terminal residues. This is the first report of a modified hGH that has anti-insulin effects greater than hGH itself.     

Growth hormone and insulin-like growth factor I treatment increase testicular luteinizing hormone receptors and steroidogenic responsiveness of growth hormone deficient dwarf mice

To test the hypothesis that insulin-like growth factor (IGF-I) is required for the in vivo development of testicular Leydig cell function, either recombinant human GH [(hGH) (1.5 micrograms/g BW) or recombinant IGF-I (1 microgram/g BW) was injected three times daily into immature Snell dwarf mice (dw/dw) and into phenotypically normal control (Dw/-) for 7 days. In dw/dw mice hGH enhanced significantly body, liver, kidney, and testicular weight. In addition, hGH increased testicular LH receptors and the acute steroidogenic response to human CG, but there was no significant effect on basal plasma testosterone or plasma LH levels. The effects of IGF-I in body and kidney weight were less pronounced than those produced by hGH, but its effects on testicular weight and LH receptors, as well as on the acute steroidogenic response to human CG, were similar to that observed after hGH treatment. In Dw/- mice hGH had no effect on either body or organ weight or on testicular function, despite the fact that it induced a significant increase in plasma IGF-I levels. These results indicated that IGF-I is able to induce the maturation of Leydig cell function and that the effects of hGH on the testis are probably mediated by IGF-I. They also suggest that the delayed puberty associated with GH deficiency or resistance is most likely related to an IGF-I deficiency.     

The role of human growth hormone in the regulation of cholesterol and bile acid metabolism

Cholesterol and bile acid metabolism was studied in 16 children with human GH (hGH) deficiency (11 with isolated hGH deficiency and 5 with multiple trophic hormone deficiency) before and after 6 months of hGH therapy. We measured plasma lipid concentrations, biliary lipid composition, and cholesterol saturation indices; calculated the bile acid pool size measured by the isotopic dilution technique using the stable isotope chenodeoxycholic-[11,12-d2] acid; and measured cholesterol and bile acid synthetic rates by sterol balance techniques. In all 16 patients, plasmas lipid concentrations were unchanged after hGH therapy; total plasma cholesterol was 182 +/- 10 (+/-SEM) mg/dl before and 179 +/- 9 mg/dl after treatment, high density lipoprotein-cholesterol was 47 +/- 2 mg/dl before and 49 +/- 3 mg/dl after treatment, low density lipoprotein-cholesterol was 112 +/- 10 mg/dl before and 111 +/- 8 mg/dl after therapy, and triglyceride was 113 +/- 13 mg/dl before and 107 +/- 10 mg/dl after hGH therapy. Biliary lipid composition and cholesterol saturation in 10 patients were similar to those in controls and unchanged with hGH therapy. Cholesterol synthesis (n = 14) was unchanged (7.6 +/- 1.4 vs. 9.6 +/- 1.2 mg/kg X day); however, bile acid synthesis (n = 15) increased from 3.1 +/- 0.4 to 4.3 +/- 0.6 mg/kg X day (P less than 0.025) after therapy. The chenodeoxycholate pool size (n = 8) was significantly reduced (P less than 0.025) before hGH treatment (416 +/- 64 mg/m2) compared to that in controls (617 +/- 45 mg/m2) and increased to 620 +/- 72 mg/m2 after hGH therapy (P less than 0.05). Chenodeoxycholate pool size expansion during hGH therapy was, at least in part, caused by an increase in hepatic bile acid synthesis. These findings suggest that hGH may indirectly modulate cholesterol metabolism through regulation of hepatic cholesterol 7 alpha-hydroxylase activity, the rate-limiting enzyme of bile acid synthesis.     

GH therapy in juvenile chronic arthritis: results of a two-year controlled study on growth and bone.

Disturbance of growth frequently occurs in children suffering from juvenile chronic arthritis (JCA). Recognition of growth impairment is important because reduced final height is one of the permanent consequences. The aim of this study was to evaluate the efficacy and safety of human GH (hGH) in growth-retarded prepubertal children with JCA. Thirty-five children were tested for GH deficiency (GHD) and randomly assigned to a study and an untreated control group; five were GH deficient and were part of the GHD group. All received glucocorticoids. The study group was treated with 1 IU/kg BW.wk hGH; the GHD group was given 0.5 IU. During 2 yr of hGH treatment growth velocity and height SD score increased compared with baseline values. There was a marked increase in growth velocity in the treated groups, but also some increase in the control group. Plasma levels of IGF-I and IGF-binding protein-3 increased with GH treatment. These results suggest that hGH might be useful in the treatment of growth impairment in JCA. GH may counteract the adverse effects of glucocorticoid therapy, but its effect is dependent on the disease activity. Long-term controlled studies are needed to determine the risks and benefits of GH therapy in JCA.     

Effect of oral clonidine, insulin-induced hypoglycemia and exercise on plasma GHRH levels in short-stature children

Human growth hormone release is affected by a variety of pharmacological and physiological stimuli. We have studied the effect of oral clonidine, insulin hypoglycemia, and exercise on plasma hGH and GHRH levels in 31 healthy short-stature children. Thirteen underwent an oral clonidine test (0.15 mg/m2), 12 an iv. insulin test (0.1 U/kg), and 6 performed exercise (running for 10 min in a defined route). GHRH-1-44 was extracted from plasma on silica columns and determined by RIA. Although all three stimuli induced a marked increase in plasma hGH levels, only clonidine induced a significant increase in plasma GHRH levels. Maximal increment in GHRH during clonidine was 6.82 +/- 1.05 pmol/l (mean +/- SEM) as compared with 0.51 +/- 0.28 and 0.53 +/- 0.62 during hypoglycemia and exercise (p less than 0.0005 and p less than 0.005), respectively. An additional 24 subjects received TRH 0.2 mg/kg iv: 8 TRH alone, 8 TRH and insulin, and 8 TRH and clonidine. Only insulin potentiated the TRH-induced TSH response with a peak of 22.0 +/- 3.2 vs 16.0 +/- 0.8 and 15.3 +/- 1.5 mU/l (p less than 0.025) for TRH alone and TRH and clonidine, respectively. It is suggested that clonidine stimulates hGH secretion mainly through an enhancement of GHRH release, whereas stress stimuli such as hypoglycemia and exercise achieve hGH release by a different mechanism, possibly inhibition of somatostatin.     

Age as a determinant of the impact of growth hormone therapy on predicted adult height

OBJECTIVE Final adult height is determined by both childhood and pubertal growth. The later is a function of growth velocity and bone maturation, and both are regulated by growth hormone. In a study of the safety and efficacy of GH therapy, we analysed the Impact of age on bone maturation and predicted adult height. PATIENTS AND METHODS The subjects were 65 male patients with GH deficiency, as diagnosed by pharmacological or physiological tests, who participated in a multi-centre trial and completed 3 years of hGH therapy. The age range at initiation of therapy was 3·1–15·7 years. Subcutaneous injections of hGH were given in a dose of 0·3 mg/kg/week, in thrice-weekly doses. Calculation of the adult height prediction was performed on annual growth parameters using the Bailey-Pinneau, TW-II and Roche methods. RESULTS The rate of pubertal advancement correlated positively with the child's age at initiation of therapy. The bone age advanced in positive correlation with chronological age, and by the end of 3 years of hGH therapy the δ-bone age/δchronological age ratio increased to 1·5 for children with an age at start of therapy of 10·7 years. During the adolescent years, the predicted gained height over 3 years of therapy declined, in correlation with age, and became negative at a therapy-initiation age of 12·9 years. CONCLUSIONS In a retrospective analysis of a group of children with heterogeneous GH secretory ability, GH induced acceleration of growth, around the age of normal puberty, advanced the age of pubertal onset and accelerated pubertal progression which, in turn, expedited bone maturation and thereby restricted predicted adult height gain from hGH therapy.     

Modulation of IGF-I receptors by exogenous hGH treatment in constitutionally short children

OBJECTIVE To study the in-vivo regulation of IGF-I binding sites on erythrocytes (RBC) following administration of growth hormone (hGH) to constitutionally short children. Recently, owing to biosynthetic techniques, treatment with hGH has been administered not only to children with GH deficiency but also to children with constitutional growth delay and with familiaf short stature. PATIENTS AND DESIGN Growth hormone (rhGH-Norditropin, Novo/Nordisk) was administered at a dose of 0 1 U/kg/ day s.c. to 11 children with constitutional short stature. Before and at 1–2 months after initiation of treatment IGF-I binding sites and serum IGF-I were determined. Erythrocytes were separated from whole blood by centrifugation over Ficoll Hypaque and used to assess IGF-I binding sites. RESULTS Serum IGF-I levels increased from 14 93 ±1 50 nmoI/I (mean±SEM) to 30 29 ±2 32 nmoI/I, with a mean difference of 15 38 + 2 21 (P= 0 00001). Concomitantly, the number of binding sites per cell decreased from 5 77 ±0.81 sites per celt (m±SEM) to 2 10 ±0 36, with a mean difference of - 3 67 ± 0 76 (P= 0.0003). The dissociation constant (K_d) also decreased from 0 47±016 MM (m±SEM) to 0.10±0 02 with a mean difference of 0 37±0.16 (P=0.02), indicating an increase in the affinity of the receptors. CONCLUSION Treatment of children with constitutional short stature with hGH raises the circulating IGF-I levels and down-regulates the IGF-I receptors: This study shows that IGF-I is capable of regulating its homologous receptor concentrations in vivo and it is suggested that the measurement of IGF-I binding sites on RBC may be used for the diagnosis of subtle states of resistance to IGF-I.     

Presence of magnetic resonance imaging abnormalities of the hypothalamic-pituitary axis is a significant determinant of the first 3 years growth response to human growth hormone treatment in prepubertal children with nonacquired growth hormone deficiency

OBJECTIVE: The factors influencing the highly variable growth response to GH treatment in GH-deficient children are not fully understood. Despite a real benefit with GH treatment in term of growth response, most of these patients attain a mean adult height below their target height and the strategy to optimise final height has to be improved. The aim of this study was to investigate whether the presence of congenital abnormalities of the hypothalamic-pituitary axis on magnetic resonance imaging (MRI) could be a determinant of the growth response in nonacquired prepubertal GH-deficient children, and to identify which pretreatment variables most significantly affect the first 3 years growth response to human GH (hGH) therapy. PATIENTS AND METHODS: The growth response to hGH treatment (0.55 +/- 0.1 IU/kg/week) was evaluated in 69 prepubertal children with nonacquired GH deficiency, according to the absence (group A: chronological age = 4.8 +/- 2.4 years, n= 37) or the presence (group B: chronological age = 3.4 +/- 2.7 years, n= 32) of developmental abnormalities on cerebral magnetic imaging and, after controlling for GH dose, age, height, height velocity (SDS) and body mass index at start of treatment, maximum stimulated GH peak concentration, GH deficiency type (isolated vs. multiple deficiency), parental height, size at birth and sex. RESULTS: After 3 years of treatment, the mean height gain was significantly higher in patients of group B vs. group A (2.2 +/- 1.3 vs. 1.6 +/- 1 SDS; P < 0.05). In a multiple regression analysis, age (r2 = 0.19, negatively correlated), pretreatment height velocity (r2 = 0.11, negatively correlated), GH dose (r2 = 0.05, positively correlated) and presence of magnetic resonance imaging developmental abnormalities (r2 = 0.05, positively correlated) were found to significantly explain 40% of the variability in growth response. CONCLUSIONS: The detection of congenital abnormalities in the hypothalamic-pituitary area on MRI is more important than the level of maximum stimulated GH to predict the growth response to hGH treatment in prepubertal nonacquired GH-deficient children. Although the persistence of GH deficiency remains to be confirmed during follow-up by reassessment of GH secretion in isolated GH-deficient patients with normal MRI findings, further studies are needed to evaluate whether an increased hGH dose in these patients could improve long-term growth response.     

Low urinary growth hormone values in patients with Turner's syndrome.

Short stature is one of the major symptoms in Turner's syndrome (TS). The cause of short stature is not clearly known at present. In this study we initially assessed GH secretory status in TS by determinations of urinary human (h) GH excretion for 2 consecutive days. Secondly, the therapeutic dose of hGH used for treatment of short stature in TS was evaluated by measurements of urinary hGH after recombinant hGH (r-hGH) injections. Twenty-four-hour urinary hGH excretion for the 2 days combined was significantly lower in patients with TS than in normal children [2.3 +/- 1.8 ng/day (n = 7) vs. 13.4 +/- 3.2 (n = 16); P less than 0.001], although four of seven patients with TS had normal GH responses to the provocative tests. The mean level of urinary hGH in TS after 2 days was comparable to that in complete GH deficiency (1.9 +/- 0.9 ng/day; n = 14) that we previously reported. Treatment with daily sc injections of 1.0 IU (0.37 mg)/kg.week r-hGH, given in seven divided doses, normalized urinary hGH excretion and induced remarkable catch-up growth in all patients with TS. These results indicate that the 24-h endogenous GH secretion in seven patients with TS is impaired. The measurement of 24-h urinary hGH excretion may prove to be useful as a marker to assess the abnormal GH secretion and the adequacy of treatment with hGH in patients with TS. The therapeutic dose of hGH in TS is approximately 0.37 mg/kg.week, given in seven divided doses. To convert international units of r-hGH to milligrams, divide by 2.7.     

Discordant immune and growth response to pituitary and biosynthetic growth hormone in siblings with isolated growth hormone deficiency type IA

Two brothers with familial isolated growth hormone deficiency type IA homozygous for the same 6.7 kb deletion on chromosome 17 including the growth hormone gene were intermittently treated with various forms of hGH for more than 7 years. While the elder brother (Patient 1) showed a good growth response to pituitary hGH, the younger one (Patient 2) developed high titre growth blocking hGH antibodies early in the course of treatment and grew only 2.2-3.9 cm/year on a hGH dose of 12-26 IU/m2 per week. When the younger brother was changed to a higher dose (33 IU/m2 per week) of biosynthetic methionyl hGH he had striking catch-up growth and he has subsequently maintained a height velocity of 10.0 cm/year for the last 2 years. During this time his antibody titres have decreased over 1000-fold. These findings demonstrate that therapy with biosynthetic methionyl hGH may provide an effective form of treatment for subjects with isolated growth hormone deficiency type IA who do not grow in response to native hGH, and imply that biosynthetic methionyl hGH may be less antigenic than pituitary derived hGH.     

Isolated growth hormone deficiency: analysis of the growth hormone (GH)-releasing hormone gene and the GH gene cluster

Isolated GH deficiency (IGHD) cannot be distinguished on the grounds of anti-human (h) GH antibodies and stunted growth response to exogenous hGH. DNA analysis was proposed to classify children with IGHD. Genomic DNA was extracted and studied by restriction endonuclease analysis after extraction from the circulating lymphocytes of 53 children with IGHD. These children included 5 pairs of siblings and 5 individuals from 10 families, whose parents (n = 20) and brothers and sisters (n = 5) were also analyzed. Twenty-five adults, including individuals from 3 families of normal height, were studied as controls. No deletion within the hGH gene cluster was identified using a [32P]hGH cDNA clone as a probe. A compound heterozygosity for a hGH-1 deletion or a mutation have not been found. The allelic frequencies for 5 common restriction fragment length polymorphisms were similar in patients and controls. The distribution and frequency of the distinct haplotypes in the hGH gene family revealed no differences between IGHD (n = 30 chromosomes) and controls (n = 48 chromosomes). No deletion or restriction fragment length polymorphisms could be found using a hGH-releasing hormone cDNA clone as a probe in patients or controls. This large volume of data gathered from a caucasian population indicates that the great majority of patients with IGHD has no structural abnormalities of the hGH gene cluster, particularly no hGH-1 gene deletion. In addition, they have no gross deletions within the hGH-releasing hormone gene.     

EFFECT OF HUMAN GROWTH HORMONE THERAPY ON HEAD CIRCUMFERENCE IN CHILDREN WITH HYPOPITUITARISM

Head circumference was measured before and during hGH therapy in fourteen children with isolated growth hormone deficiency (IGHD) and in twenty-one children with multiple pituitary hormone deficiencies (MPHD). In both groups there was a retardation in growth of the neurocranium, more marked in the children with IGHD, which was less than the retardation in linear height. In the group with IGHD, initiation of hGH therapy before a chronological age of 5 and a bone age of 3 had been reached led to a rapid catch-up in cranial growth with normalization of the head size. In older children the induction of head growth was similar to that achieved by the long bones but without a true catch-up phenomenon. In three adults with hereditary IGHD without therapy or with irregular treatment during late puberty, the head circumference was below normal range. In view of the possible role played by development of brain tissue upon cranial size, the importance of early diagnosis and initiation of therapy in infants and young children with a deficiency of hGH is stressed.     

Phenotypic heterogeneity in familial isolated growth hormone deficiency type I-A

We studied an Argentinian family of Spanish ancestry in which the parents are of normal height and three of their four children have isolated GH deficiency type I-A. Restriction endonuclease analysis of DNA isolated from leukocytes was done using 32P-labeled human GH (hGH) cDNA sequences as a probe. The three siblings were homozygous, while their parents and the remaining sibling were heterozygous for a deletion of about 7.5 kilobases DNA, which included the normal hGH gene. The phenotype of the affected subjects differed in several respects. There was variation between the homozygotes in birth length and height before hGH treatment and growth responses during long term hGH treatment. Furthermore, heterozygotes in this family had normal height despite their diminished hGH responses to provocative tests.