Survey of clinical practice: growth hormone use during illness.

Prior to the 1999 National Cooperative Growth Study (NCGS) meeting, a postal card survey was conducted of the NCGS investigators about their current practices regarding continuation of growth hormone (GH) therapy during intercurrent illnesses. The survey results were subsequently compared with responses to the same questions obtained from NCGS investigators who attended lectures at the NCGS meeting describing the physiology and effects of GH in critically ill patients. Comparing results from the two surveys, there were no observed differences in the responses with respect to practices relative to the intercurrent illnesses treated at home. The percentage of NCGS investigators who indicated that they would stop GH treatment during more serious illnesses was greater following attendance at the lectures.

Genetic disorders of calcium and phosphorus metabolism.

The genetic control of calcium, phosphorus, cartilage, and bone metabolism is discussed, and many of the genes involved in this process are described. Mutations in these genes that lead to the clinical disorders associated with hypercalcemia, hypocalcemia, rickets, and osteochondrodystrophies are delineated.

Severe Lhermitte-Duclos disease with unique germline mutation of PTEN.

Germline mutations in the PTEN gene have recently been identified in some individuals with Cowden disease (CD), Lhermitte-Duclos disease (LDD), and Bannayan-Zonana syndrome. We report on a patient with CD and LDD in whom a unique de novo germline missense mutation is present in the PTEN gene. Direct sequence analysis detected a transitional change (T-->C) at nucleotide 335, resulting in substitution of the amino acid proline for leucine. The mutation is in exon 5, which has been proposed as a "hot-spot" for germline mutations. Comparison of this patient's clinical course with the previously reported cases of CD and LDD shows more extensive and more severe clinical findings than reported previously. Findings in this patient contribute to the current understanding of germline PTEN mutations and clinical outcome.

A spun-column assay for determination of leptin binding in serum.

Serum collected from 27 patients was assayed simultaneously using a spun-column assay (SPC) and a traditional exclusion gel-filtration assay (GFC) to determine specific leptin binding. The levels of serum leptin binding determined by either assay correlated inversely with serum leptin levels (SPC, r = 0.63, P < 0.001; GFC, r = 0.79, P < 0.0001). Although specific leptin binding as determined by the traditional exclusion gel-filtration assay was generally higher than that obtained by the spun-column assay (mean = 18.3% vs 14.0%, P < 0. 02, respectively); the values obtained between the two assay methods were highly correlative (r = 0.89, P < 0.0001). By varying either the amount of 125I-leptin or the amount of competitor, analysis was carried out using the spun-column assay to determine the intrinsic properties of serum leptin binding. Results yielded a Kd = 0.3 nM, where each variable amount of leptin or competitor was carried out in duplicate. The complete analysis was carried out in the time that it typically takes for a single sample determination by the traditional exclusion gel-filtration assay. We conclude that the "spun-column" assay is a useful method for rapid and accurate quantification of leptin binding in serum.

Optimizing estrogen replacement treatment in Turner syndrome.

Estrogen has a biphasic effect on growth, stimulatory at low doses but inhibitory at higher doses. Therefore, designing optimal sex hormone replacement treatment in girls with Turner syndrome (TS) who are being treated with growth hormone (GH) involves considering the dose and form of the estrogen as well as the route and timing of its administration. We report here a preliminary analysis of a study to test the concept that an optimal estrogen replacement regimen should consist of estradiol administered in a low dose by a systemic route. The study population consisted of 9 girls with TS who had been treated with GH for 6 or more months. When the girls were 12 to 15 years old, we added depot estradiol at a monthly intramuscular dose of 0.2 mg and increased the dose at 6-month intervals to 0.4, 0.6, and, in 7 of the girls, 0.8 mg. We compared the results in these subjects with those in a matched group of 37 patients with TS in whom routine estrogen treatment had been started at similar ages and who were treated with a similar course of GH therapy. The gain in height at 2 years was 2.6 cm greater in those who were treated with depot estradiol than in those who were treated with routine estrogen. The bone age in the patients who were treated with depot estradiol increased in proportion to their chronologic age, suggesting that this difference indicates an increase in their predicted adult height. We conclude that using very low doses of systemic estradiol to induce puberty before the age of 15 years in girls with TS who are treated with GH, instead of using routine estrogen therapy, can result in increased final heights.

The role of serial sampling in the diagnosis of growth hormone deficiency.

We analyzed 12-hour serial sampling of growth hormone (GH) levels in two cohorts of short children: 96 children referred to a university endocrine clinic or studied on a research protocol and 825 children in the National Cooperative Growth Study of children treated with exogenous GH. The mean 12-hour GH levels correlated with growth velocity in 60 children with normal height and growth velocity in the university study, and this correlation was stronger in the boys. The testosterone levels also correlated with growth velocity and mean 12-hour GH levels in the boys. The mean 12-hour GH levels were lower in a group of 36 children with idiopathic short stature than in the control subjects, as were the peak GH levels within 1 hour after the onset of sleep and the insulin-like growth factor I levels. In the National Cooperative Growth Study cohort, pooled 12-hour GH levels were lower in the group with idiopathic GH deficiency (n = 300) than in the group with idiopathic short stature (n = 525), but the difference was not significant. The duration of GH treatment was the most significant predictor of change in the height SD score in both groups. Indices of spontaneous secretion of GH were not predictive of the response to GH treatment, nor were the results of provocative GH testing, the responses to GH treatment being similar in both groups over time. We conclude that the results of GH testing must be interpreted for each patient and that several testing modalities may be helpful in finding GH insufficiency that originates at various levels of the somatotropic axis.

Interleukin 1beta mediated calciotropic activity in serum of children with juvenile rheumatoid arthritis.

OBJECTIVE: To detect the presence and source of calciotropic activity in the serum of children with juvenile rheumatoid arthritis (JRA). METHODS: Metabolic evaluation of an adolescent with polyarticular JRA and hypercalcemia/hypercalciuria included testing with a bone disc bioassay. The bioassay detects calciotropic activity (increased bone resorption or reduced bone formation) in serum. Interleukin 1 receptor antagonist (IL-1RA) was added to patient sera to test the role of IL-1beta. The results in this index case prompted additional study in 9 children with JRA. Correlation of calciotropic activity with disease activity score, erythrocyte sedimentation rate (ESR), and urinary calcium excretion was by Spearman rank correlation. RESULTS: Calciotropic activity was found in 2 consecutive samples from the index patient. This activity was eliminated by addition of IL-1RA (p < 0.001 compared to serum alone). Testing of the other 9 children showed calciotropic activity at least once in 7/9 and 10/15 samples studied. Addition of IL-1RA completely (6/8) or partially (2/8) neutralized calciotropic activity (p < 0.001 compared to serum alone) in the specimens available for testing. Calciotropic activity did not significantly correlate with disease activity score, ESR, or urine calcium. CONCLUSION: Our data indicate the presence of IL-1beta mediated calciotropic activity in the sera of children with JRA, and suggest a role for IL-1beta in JRA associated osteopenia.

Effect of long-term recombinant growth hormone therapy in children--the National Cooperative Growth Study, USA, 1985-1994.

Over a 9-year period (1985-1994) approximately 20,000 children received recombinant human growth hormone (rhGH) while enrolled in the National Cooperative Growth Study (NCGS), an observational, longitudinal study designed to monitor the long term efficacy and safety of rhGH administered to children in North America. Forty-four percent of the patients had idiopathic growth hormone deficiency (IGHD), 13.8% organic GHD (OGHD), 25% idiopathic short stature (ISS), 9.9% Turner's syndrome (TS), and 7.3% miscellaneous disorders. Eighty-five percent of the patients enrolled were Caucasian, and approximately two-thirds of the non-Turner patients were male. For the subset of patients treated for at least 4 years and who were prepubertal throughout this period (IGHD N=308, OGHD N=93, ISS N=169, TS N=82), mean growth rates increased in all patient categories and remained at or above pretreatment growth rates through 4 consecutive years of therapy with rhGH. Growth rates during administration of rhGH were greater in children in whom the pretreatment maximum stimulated GH concentration was < or =3 microg/l. Patients treated with 6 or 7 doses of rhGH each week grew more rapidly than did those receiving thrice weekly dosages, although the ratios of the increment in bone age to the increment in height age after two years of therapy were similar in the two treatment regimens. For patients treated with rhGH for 7 consecutive years, the mean height standard deviation scores increased by 2.5 in IGHD (N=169), 2.0 in OGHD (N=50), 1.9 in ISS (N=69), and 1.3 in TS (N=19), but remained below target heights in all categories. It is concluded that administration of rhGH increases growth rates in patients with IGHD, OGHD, ISS, and TS, and that this stimulatory effect can persist for at least 4 years.

Demonstration of a leptin binding factor in human serum.

Serum leptin levels are elevated in subjects with exogenous obesity, indicating that obesity is associated with leptin resistance. Since in man no abnormalities have yet been found in either the genes for leptin or its receptor, the mechanism of leptin resistance in obesity remains unknown. To determine if resistance might be related to leptin binding by a serum component, we assessed the carrier status of leptin in serum. The presence of a specific leptin binding factor in human serum has been established by (1) demonstrating [125I]-leptin binding to a serum component that is saturable and specifically displaceable only by unlabeled leptin and not by human growth hormone, pork insulin, insulin-like growth factors I and II, luteinizing or follicle stimulating hormones, transforming growth factor-beta 1, interleukin-6, or leukemia inhibiting factor; (2) fractionating the leptin bound serum complex and the serum leptin binding component on a molecular sieving column revealing a mass of approximately 450 kDa; and (3) identifying an inverse correlation between the concentration of serum leptin and the quantity of the leptin binding component. It is suggested that binding of leptin by this serum component may influence the physiologic response to leptin.

Evaluation of the clinical utility of the ultrasensitive immunofluometric assay for growth hormone (GH) and of the cortisol secretory pattern in prediction of the linear growth response to treatment with GH.

OBJECTIVES: To evaluate the utility of an ultrasensitive IFMA for human 22 kDa GH in assessment of GH secretion and prediction of the linear growth response to exogenous GH. METHODS: Utilizing Delfia reagents supplied by Wallac-OY, an ultrasensitive IFMA for GH was established. Serum GH concentrations from 15 children/adolescents undergoing 24 hour GH secretory profiles with sampling at 20 minute intervals were analyzed by both IFMA and RIA. Cortisol values were also measured. Twelve children were later treated with GH. The 24 hour GH and cortisol secretory profiles were analyzed by the Cluster program and the relationships of these profiles to the linear growth response to exogenous GH determined. RESULTS: The sensitivity of the IFMA for GH relative to a zero standard was 0.005 ng/ml; intra-assay coefficients of variation ranged from 12% at a GH concentration of 0.005 ng/ml to 4% at 0.038 ng/ml; interassay coefficients of variation ranged from 34% at a GH concentration of 0.005 ng/ml to 10.5% at 2.7 ng/ml and to 2.7% at 12.7 ng/ml. Above assay sensitivity, there was good correlation between GH concentrations determined by IFMA and those by IRMA and RIA (r = 0.998 and 0.992 respectively). The number of GH secretory peaks identified by IFMA was significantly greater than that detected by RIA (10.6 +/- 3.2 [SD] vs 6.7 +/- 3.3/24 hours, p = 0.0001 by paired t-test). There were few significant relationships between any parameter of GH secretion measured by RIA or IFMA (peak GH pulse amplitude, percent increase in amplitude, area under the peak, interpeak interval) and the pretreatment growth rate, the growth velocity while receiving GH therapy, or the increment in growth rate during administration of GH. The number of GH secretory peaks determined by RIA correlated weakly with the pretreatment growth rate. There was no meaningful relationship between the serum concentrations of cortisol and GH-IFMA. Peak GH concentrations and nadir cortisol values were exactly coincident in 15.7% (25/159); 42.8% of nadir cortisol values coincided with or were within +/- 20 minutes of peak GH values (68/159). However, there was no relationship between the number of cortisol secretory peaks, the pooled 24 hour and nocturnal concentrations of cortisol and the pretreatment growth velocity, the growth rate or increment in growth velocity during administration of GH. CONCLUSIONS: Despite the increased sensitivity of the IFMA and its ability to detect pulsatile GH secretion heretofore unidentified, data from this GH assay were not useful in predicting first year growth rate during administration of GH. The secretory pattern of cortisol was not helpful in predicting the growth response to GH.

Autoimmune hyperthyroidism in prepubertal children and adolescents: comparison of clinical and biochemical features at diagnosis and responses to medical therapy.

We explored our clinical impression that young children with autoimmune hyperthyroidism are more thyrotoxic at presentation and require a longer course of medical therapy than do adolescents to achieve remission. A retrospective chart review of clinical and biochemical data at presentation and response to therapy in 32 prepubertal (PREPUB) and 68 pubertal (PUB) children and adolescents with autoimmune hyperthyroidism was undertaken. Initial therapy included prophylthiouracil or methimazole in all but 11 patients who chose radioactive iodine (131I); 30 additional patients ultimately chose 131I or surgery after an initial period of medical therapy. In PREPUB children there were significantly longer duration of symptoms (7.8+/-7.7 months) and higher serum concentrations of triiodothyronine (T3) 708+/-330 ng/dL) at presentation than in the PUB group (4.7+/-3.4 months; p < .05) (537+/-197 ng/dL; p < .01). Duration of symptoms correlated negatively with chronologic age (r = -0.24; p < .02) but not with T3 or thyroxine (T4) levels (p = .1). PUB children had significantly higher titers of thyroid microsomal antibodies (positive dilution factor 1:6022+/-14572) than did PREPUB children (1:592+/-1226; p < .05). There was a higher familial incidence of thyroid disease in boys (80%) than in girls (64%) (p < .02). The duration of medical therapy was significantly longer (3.5+/-2.9 years) in PREPUB children compared to the PUB group (2.2+/-1.8 years) (p < .05). Only 17% of PREPUB treated 5.9+/-2.8 years compared with 30% of PUB treated 2.8+/-1.1 years achieved a 1-year remission after stopping antithyroid medication (percentage between groups, p < .01; years of treatment, p < .05). The median time to remission after medical therapy was 8 years in PREPUB and 4 years in PUB (p < .02). PREPUB children continued to remit after prolonged medical therapy (>6 years) whereas PUB patients did not. Total treatment length correlated negatively with chronological age (r = -0.26; p < .05) and positively with T4 and T3 concentrations at diagnosis (r = 0.31; p < .01). The diagnosis of hyperthyroidism is delayed in prepubertal children compared to adolescents. This delay may contribute to the higher T3 levels observed in this group at presentation. Prepubertal children also appear to require longer medical therapy to achieve a lower rate of remission, but do continue to remit after prolonged treatment. These differences in response to therapy should be considered when discussing therapeutic options with the family.

Linkage disequilibrium analysis in young populations: pseudo-vitamin D-deficiency rickets and the founder effect in French Canadians.

Pseudo-vitamin D-deficiency rickets (PDDR) was mapped close to D12S90 and between proximal D12S312 and distal (D12S305, D12S104) microsatellites that were subsequently found on a single YAC clone. Analysis of a complex haplotype in linkage disequilibrium (LD) with the disease discriminated among distinct founder effects in French Canadian populations in Acadia and in Charlevoix-Saguenay-Lac-Saint-Jean (Ch-SLSJ), as well as an earlier one in precolonial Europe. A simple demographic model suggested the historical age of the founder effect in Ch-SLSJ to be approximately 12 generations. The corresponding LD data are consistent with this figure when they are analyzed within the framework of Luria-Delbrück model, which takes into account the population growth. Population sampling due to a limited number of first settlers and the rapid demographic expansion appear to have played a major role in the founding of PDDR in Ch-SLSJ and, presumably, other genetic disorders endemic to French Canada. Similarly, the founder effect in Ashkenazim, coinciding with their early settlement in medieval Poland and subsequent expansion eastward, could explain the origin of frequent genetic diseases in this population.