Type 2 diabetes in children

The emerging epidemic of type 2 diabetes (T2DM) in young people reflects increasing rates of obesity and parallels the increasing frequency of T2DM in adults. As in adults, T2DM in children is part of the insulin resistance syndrome that includes hyperandrogenism seen as premature adrenarche and polycystic ovary syndrome, hypertension, dyslipidemia, and other atherosclerosis risk factors. Recent studies in children document risk factors for T2DM, and associated cardiovascular risk factors, including obesity, family history, diabetic gestation, and underweight or overweight for gestational age. Genetically determined insulin resistance or limited beta-cell reserve has been demonstrated in high-risk individuals, including first-degree relatives of girls with premature adrenarche. This genetic background, considered advantageous in a feast-and-famine existence (the thrifty genotype), is rendered detrimental with abundant food and physical inactivity, a lifestyle demonstrated to be typical of families of children with T2DM. The increasing incidence of T2DM in children and adolescents threatens to become a major public health problem. Risk factors for cardiovascular disease, hypertension, hyperlipidemia, and microalbuminuria are present at diagnosis of T2DM in Native American adolescents, indicating that insulin resistance has been present for some time before the diagnosis of diabetes was made. Case finding is likely to be beneficial in high-risk youths. Treatment is the same as that of adults. The only data on use of oral hypoglycemic agents in children have been with metformin. Community and governmental efforts to educate all children and their parents about the need for physical activity and dietary modification are essential to control this epidemic.

Positional dissociation between the genetic mutation responsible for pseudohypoparathyroidism type Ib and the associated methylation defect at exon A/B: evidence for a long-range regulatory element within the imprinted GNAS1 locus

Pseudohypoparathyroidism type Ib (PHP-Ib) is a paternally imprinted disorder which maps to a region on chromosome 20q13.3 that comprises GNAS1 at its telomeric boundary. Exon A/B of this gene was recently shown to display a loss of methylation in several PHP-Ib patients. In nine unrelated PHP-Ib kindreds, in whom haplotype analysis and mode of inheritance provided no evidence against linkage to this chromosomal region, we confirmed lack of exon A/B methylation for affected individuals, while unaffected carriers showed no epigenetic abnormality at this locus. However, affected individuals in one kindred (Y2) displayed additional methylation defects involving exons NESP55, AS and XL, and unaffected carriers in this family showed an abnormal methylation at exon NESP55, but not at other exons. Taken together, current evidence thus suggests that distinct mutations within or close to GNAS1 can lead to PHP-Ib and the associated epigenetic changes. To further delineate the telomeric boundary of the PHP-Ib locus, the previously reported kindred F, in which patient F-V/51 is recombinant within GNAS1, was investigated with several new markers and direct nucleotide sequence analysis. These studies revealed that F-V/51 remains recombinant at a single nucleotide polymorphism (SNP) located 1.2 kb upstream of XL. No heterozygous mutation was identified between exon XL and an SNP approximately 8 kb upstream of NESP55, where this affected individual becomes linked, suggesting that the genetic defect responsible for parathyroid hormone resistance in kindred F, and probably other PHP-Ib patients, is located >or=56 kb centromeric of the abnormally methylated exon A/B. A region upstream of the known coding exons of GNAS1 is therefore predicted to exert, presumably through imprinting of exon A/B, long-range effects on G(s)alpha expression.

Changes in frequency and severity of limited joint mobility in children with type 1 diabetes mellitus between 1976-78 and 1998

OBJECTIVE

Limited joint mobility (LJM), the earliest clinically apparent long-term complication of type 1 diabetes mellitus, is a risk indicator for microvascular complications, and its appearance is primarily affected by long-term metabolic control. We hypothesized that the prevalence of LJM had decreased during the past 20 years.

STUDY DESIGN

We examined 312 subjects with type 1 diabetes mellitus, aged 7 to 18 years, using the same examination method and criteria as in studies of 515 subjects in this age group carried out between 1976 and 1978 for whom primary data were available, including age, duration of diabetes, and LJM stage. Statistical analyses included exact chi(2) tests, independent sample t tests, and unconditional logistic regression.

RESULTS

There was a >4-fold reduction in frequency of LJM between 1976-78 and 1998 (31% vs 7%, P <.001), with a decrease in the proportion having moderate or severe LJM (35% vs 9%, P =.025).

CONCLUSIONS

These findings confirm the hypothesis that the prevalence of LJM has decreased, most likely the result of improved blood glucose control during the past 2 decades.

New developments in type 1 (insulin-dependent) diabetes

The Diabetes Control and Complications Trial has conclusively demonstrated that improved metabolic control leads to reduction in the rate of microvascular complications of diabetes. In order to allow patients to achieve improved metabolic control, much research has focused on improved methods of glucose monitoring and more physiologic ways of insulin delivery. The 2 most promising methods of minimally invasive blood glucose monitoring are the Glucowatch, using the technique of reverse iontophoresis to measure interstitial fluid glucose levels every twenty minutes and an implantable sensor, in which a catheter resembling that used for insulin delivery through a pump is impregnated with glucose oxidase at the tip. This device monitors blood sugars every few minutes, but like a holter monitor, must be downloaded in the physician's office. Still under development are (1) implantable subcutaneous sensors with a high and low blood glucose alarm and (2) sensors in which the patient will be able to download the data using a home PC. Advances in insulin delivery have included the availability of new insulin analogs which more closely simulate endogenous insulin release, with rapid acting analogs simulating the increase in insulin production that normally occurs after meals. Phase III clinical trials are in progress of a long-acting basal insulin without peak actions to simulate the low dose continuous production of the insulin which normally inhibits hepatic glucose production. In addition, use of the insulin pump has increased markedly since publication of the DCCT with the greatest increase being among adolescents. In addition to advances in treatment of diabetes, research has continued on curing the disease using islet cell transplantation and preventing the disease with agents such as insulin (DPT-1 Trial) and nicotinamide (ENDIT). This article provides an overview of recent advances in diabetes management and prevention.

An initial investigation of validation of the Matrix Analogies Test-Expanded Form in Ecuador

This is a first preliminary study of the validity and reliability of the Matrix Analogies Test--Expanded Form in South America. Participants were 104 Spanish-speaking children between the ages of 5 and 17 years living in Ecuador. Values of Cronbach alpha ranged from .87 to .92 for the 4 groups of items and was .95 for the total score. Raw scores on the MAT increased across ages. Scores of boys did not differ significantly from those of girls. Total test scores correlated significantly with scores on the Raven Standard Progressive Matrices (r = .62, p < .005; r = .82 before controlling for age). A principal factor analysis conducted to provide evidence of the test's construct validity indicated that all four sets of items loaded substantially on one unrotated factor, presumed to be g. In sum, these results suggest that the test is a valid and reliable nonverbal measure of general cognitive ability in this population.

Physiology and disorders of the growth hormone receptor (GHR) and GH-GHR signal transduction

GH exerts its actions through binding with two receptor molecules at the cell surface and interaction with Janus kinase and signal transducers and activators of transcription, and other likely effectors to stimulate metabolic effects and IGF synthesis. The circulating GH binding protein is the proteolytic product of the cell surface receptor and serves as a marker of receptor number and function. Thirty-six distinct mutations of the receptor in the extracellular and transmembrane domains cause a clinical picture of severe GH/IGF-I deficiency, whereas two dominant negative mutations of the intracellular domain result in a milder clinical syndrome. These mutations have provided insight into the physiology of the GH receptor. A few patients have been described with what appears to be primary GH insensitivity due to defective signal transduction by the GH-GH-receptor complex. Clinical and biochemical features of primary GH insensitivity are not a function of genotype, with as much variability in a genetically homogeneous population as in a heterogeneous one. Except for those dominant negative mutations where co-transfection of the mutant GH receptor gene with wild-type receptor gene has been informative, evidence for an effect of a single mutant allele remains speculative. Treatment of GH receptor deficiency with recombinant human IGF-I suggests that the absence of a direct effect of GH limits growth response.

Treatment of type 2 diabetes mellitus in children and adolescents

The treatment of type 2 diabetes mellitus (DM) is directed at decreasing insulin resistance and increasing insulin secretion. alpha-Glucosidase inhibitors slow carbohydrate absorption, resulting in reduced postprandial hyperglycemia; thiazolidinediones increase insulin sensitivity, especially in muscle and adipocytes; metformin decreases hepatic gluconeogenesis; sulfonylureas result in prolonged increases in insulin secretion; and meglitinide causes rapid, short-lived increases in insulin secretion. A survey of 130 pediatric endocrinology practices in the USA and Canada indicated that 48% of children with type 2 DM were treated with insulin and 44% with one or more oral hypoglycemic agents (OHA). Of those treated with OHA, 71% received metformin, 46% sulfonylureas, 9% thiazolidinediones and 4% meglitinide. Similarly, in the three university-based diabetes centers in Florida, 50% of the children with type 2 DM were treated with OHA. Treatment is based on symptoms at presentation. Patients identified on routine testing are often treated with exercise and diet alone. Those who are mildly symptomatic at onset are often started on OHA. Patients with substantial ketosis, ketoacidosis or markedly elevated blood glucose levels are initially treated with insulin, followed by a tapering of the dose and the addition of an OHA after blood glucose control is established and symptoms subside. There are no studies of the efficacy or compliance with treatment for type 2 DM in adolescents. Treatment is currently based on the clinical experience with adults. Controlled clinical trials in children are essential.

Is short stature a handicap? A comparison of the psychosocial functioning of referred and nonreferred children with normal short stature and children with normal stature

OBJECTIVES

Normal short stature (NSS), defined as height below the 5th percentile for age and sex norms that is not due to illness, hormonal deficiency, or part of a dysmorphic syndrome, has been thought to have a deleterious effect on psychosocial functioning based on observations of referred populations. Recent studies of nonreferred children with NSS, however, have demonstrated normal function. This study directly compared the psychosocial functioning of referred children with NSS, nonreferred children with NSS, and children with normal stature.

STUDY DESIGN

Participants, 90 children (46 boys, 44 girls) between 6 and 12 years of age (mean, 9. 6 years), were administered intelligence and achievement tests. Parents and teachers assessed adaptive and problem behaviors. Family adaptability and cohesiveness were measured.

RESULTS

Intelligence and achievement for referred and nonreferred children with NSS were average. Referred children with NSS were reported to have more externalizing behavior problems and poorer social skills than nonreferred children with NSS and children in the control group. Family adaptability and cohesiveness were comparable across groups.

CONCLUSIONS

Children with NSS have normal psychosocial function, and results suggest that externalizing behavior problems, attention problems, and poor social skills in children referred to clinics for NSS are inappropriately attributed to short stature.

IGF-I deficiency due to GH receptor deficiency

IGF-I deficiency may be primary due to defective synthesis, or secondary to GH receptor deficiency (GHRD) or defects in transduction of the GH-GHR signal. Cloning and sequencing of the GHR led to recognition that circulating GH binding protein (GHBP) was structurally identical to the extra-cellular domain of the GHR, and the identification of 33 mutations of the GHR in approximately half of the 250 patients that have been reported. This review explores the information provided about GHR function by various mutations, the population distribution of GHRD, the effects of this condition on mortality, growth, development, and metabolism, the effects of replacement therapy with recombinant human IGF-I, diagnostic issues, and the question of partial GH resistance.

Natural history of growth hormone receptor deficiency

This review discusses the natural history of growth hormone receptor deficiency (GHRD) in relation to epidemiology, mortality, growth, certain aspects of body composition, and intellectual development. The majority of affected individuals are of Semitic origin and 90% come from the Indian peninsula, the Middle East, or elsewhere in the Mediterranean. There is a twofold increased mortality before the age of 7 years for children with GHRD. Affected adults may have increased cardiovascular risk resulting from increased total cholesterol and low-density lipoprotein cholesterol, unrelated to adiposity or insulin resistance. Intrauterine growth is affected minimally, if at all. Within a genetically homogeneous population in Ecuador, postnatal growth effects are as variable as in a large genetically heterogeneous population. There is no influence of parental heights. Areal bone mineral density is reduced in adults with GHRD, but estimated volumetric bone density (bone mineral apparent density) is normal. Intellectual development is unaffected by GHRD.

Emerging epidemic of type 2 diabetes in youth

This review considers the epidemiologic evidence of an increasing incidence of type 2 diabetes in youth, the classification and diagnostic issues related to diabetes in young populations, pathophysiologic mechanisms relevant to the increasing incidence, the role of genetics and environment, and the community challenge for prevention and treatment. Type 2 diabetes in youth has been recognized to be frequent in populations of native North Americans and to comprise some 30 percent of new cases of diabetes in the 2nd decade of life, largely accounted for by minority populations and associated with obesity. Among Japanese schoolchildren, type 2 diabetes is seven times more common than type 1, and its incidence has increased more than 30-fold over the past 20 years, concomitant with changing food patterns and increasing obesity rates. The forms of diabetes seen in children and youth include typical type 1, occurring in all races; type 2, seen predominantly in minority youth; atypical diabetes, seen as an autosomal dominantly transmitted disorder in African-American populations; and maturity-onset diabetes of the young (MODY), seen rarely and only in Caucasians. Of the nonautoimmune forms of diabetes seen in youth, only type 2 diabetes is increasing in incidence. Proper classification requires consideration of onset (acute/severe versus insidious), ethnicity, family history, presence of obesity, and if necessary, studies of diabetes related autoimmunity. Insulin resistance predicts the development of diabetes in Pima Indians, in offspring of parents with type 2 diabetes, and in other high-risk populations. African-American children and youth have greater insulin responses during glucose tolerance testing and during hyperglycemic clamp study than do whites. There is also evidence of altered beta-cell function preceding the development of hyperglycemia. Of particular interest is the evidence that abnormal fetal and infantile nutrition is associated with the development of type 2 diabetes in adulthood. The thrifty phenotype hypothesis states that poor nutrition in fetal and infant life is detrimental to the development and function of the beta-cells and insulin sensitive tissues, leading to insulin resistance under the stress of obesity. The thrifty genotype hypothesis proposes that defective insulin action in utero results in decreased fetal growth as a conservation mechanism, but at the cost of obesity-induced diabetes in later childhood or adulthood. The vast majority of type 2 diabetes in adults is polygenic and associated with obesity. Monogenic forms (MODY, maternally transmitted mitochondrial mutations) are rare, but are more likely to appear in childhood. Linkage studies of the common polygenic type 2 diabetes have emphasized the heterogeneity of the disorder. The prevention and treatment of type 2 diabetes in children and youth is a daunting challenge because of the enormous behavioral influence, difficulty in reversing obesity, and typical nonadherence in this age-group. The emerging epidemic of type 2 diabetes in the pediatric population, especially among minorities whose proportion in the U.S. population is increasing, presents a serious public health problem. The full effect of this epidemic will be felt as these children become adults and develop the long-term complications of diabetes.

Clinical and biochemical phenotype of familial anterior hypopituitarism from mutation of the PROP1 gene

We have investigated the largest family with PROP1 deficiency reported to date. Eight patients, aged 17-40 yr, in two sibships with possibly related mothers but no parental consanguinity were 109-137 cm in height (-8.8 to [minus]5.9 SD score) and sexually immature. None had received hormonal therapy. Affected individuals had similarities to and significant differences from patients with insulin-like growth factor I (IGF-I) deficiency due to GH receptor deficiency (GHRD) and normal thyroid function and sexual maturation. The differences from patients with GHRD include normal hand and foot length in seven of eight, normal arm span with relatively long legs, and persistence of extremely low levels of IGF-I into adulthood; similarities include the degree of growth failure, frequent but not uniform increased body weight for height or body mass index, and the presence of limited elbow extensibility and blue scleras in six of eight. Three patients had markedly increased sella turcica area for height age and bone age, determined from lateral skull films. The degree of sellar enlargement is variable in these two sibships. Serum GH concentrations were 0.1 ng/mL or less after clonidine ingestion. Other results were: IGF-I, 3-11 ng/mL (normal, 114-492); IGF-II, 185-299 ng/mL (normal, 358-854); IGF-binding protein-1 (IGFBP-1), 12-200 ng/mL (normal, 13-73); IGFBP-2, 60-384 ng/mL (normal, 55-480); and IGFBP-3, 400-600 ng/mL (normal, 2000-4000). The very low IGF-I and normal IGFBP-1 and -2 levels differ from findings in adults with GHRD. The GH-binding protein concentration was 58-799 pmol/L, with two patients above the normal range of 66-306. LH and FSH levels were very low, with no sex differences between serum levels of estradiol (3-6 pg/mL) and testosterone (3-10 ng/dL). PRL levels all were below normal. Serum concentrations of cortisol were normal. Serum T4 levels were uniformly low (<0.2-0.5; normal, 0.8-2.7 ng/dL), free T3 values were less than normal in seven of eight subjects, and total T3 concentrations were below normal in five of eight, but TSH levels were normal (0.58-2.18; normal, 0.4-4.2 mU/L). DNA specimens from affected individuals in each sibship were homozygous for a 2-bp deletion in exon 2 of the PROPI (Prophet of Pit-I) gene, which causes a shift of reading frames and results in a translational stop signal at codon 109. The mutant protein, when expressed in vivo lacks DNA-binding and transcriptional activation functions. The consequences of the PROPI abnormality in this and other kindreds include gonadotropin deficiency as well as the expected deficiencies in products of Pit-I-dependent somatotrophs, lactotrophs, and thyrotrophs. The severity of the hormone deficiency phenotype is compatible with the complete loss of PROP1 activity.

Stature of Russian children with isolated cleft lip and palate

OBJECTIVE

To evaluate the stature of Russian children with cleft lip and palate (CLP).

DESIGN

One hundred twelve Russian children predominantly with repaired unilateral CLP 4 through 10 years of age underwent studies including height measurement, physical examinations, and record review. Children with health concerns that could affect growth were excluded. U.S. growth data from the National Center for Health Statistics (NCHS) and Russian parental heights were used in the absence of Russian growth norms.

RESULTS

Based on U.S. norms, the distribution curve for heights for the Russian children was largely confined to the +1 to -1 standard deviation (SD) range. Sixty-two percent of the Russian children had heights below the 50th percentile for American female and male children of the same age. The proportion of children found outside the +1 to -1 SD range approximated the proportion expected statistically for the general population, with 14.4% < -1 SD (16th percentile) and 12% > +1 SD (84th percentile). A total of 3.6% of the children ranked below the third percentile, which is close to the expected 3%. Russian parents' (n = 209) mean heights were 0.5 SD below NCHS's 50th percentile values for adults.

CONCLUSION

These results indicate that there is no increased risk of true short stature in 4- to 10-year-old Russian children with repaired CLP.

Lessons from the genetics of laron syndrome

In the decade since the cloning and sequencing of the growth hormone receptor (GHR) and the recognition that the circulating GH-binding protein (GHBP) is structurally identical to the extracellular domain of the GHR, 34 mutations have been described. These include one deletion, eight nonsense mutations, eleven missense mutations, four frameshift mutations and ten splice mutations. More than half of the 131 patients with Laron syndrome whose molecular defects have been identified comprise the Ecuadorian cohort who share a single splice mutation. Variable expression of different homozygous or compound heterozygous defects of the GHR is no greater than the variation within a genetically homogeneous population. Some features, such as birth size and intelligence, are unlikely to be affected by GHRD. Greater understanding of the genetics, physiology, and clinical expression of abnormalities in the GH-GHR-IGF-I (insulin-like growth factor I) axis necessitates a reconsideration of the classification of GH insensitivity (GHI).

Stature in Ecuadorians heterozygous for growth hormone receptor gene E180 splice mutation does not differ from that of homozygous normal relatives

Heterozygosity for certain mutations of the GH receptor (GHR) gene has been proposed as the cause of partial resistance to GH, and there has been a recent demonstration of a dominant-negative effect of such a mutation in a mother and child. To examine the effect of heterozygosity in a large genetically homogeneous population with GHR deficiency, in which a substantial number of heterozygous (carrier) subjects and homozygous normal individuals can be compared, we studied a population in Ecuador in which 70 individuals with GHR deficiency were homozygous for the E180 splice mutation. We found that 58 heterozygous relatives of probands were not significantly shorter than 37 homozygous normal relatives [SD score (SDS) for height -1.85 +/- 1.04 (SD) vs. -1.55 +/- 0.96, P > 0.10]. When only those families with both homozygous normals and carriers were compared, the 33 heterozygous and 29 normal relatives did not differ significantly in height SDS (-1.98 +/- 1.07 vs. -1.77 +/- 0.91, P > 0.3). If heterozygosity for the E180 splice mutation were to influence stature, heights of heterozygous parents of probands would be expected to correlate with those of probands and of carriers who are their offspring and not with heights of their homozygous normal children. Parental height SDS did not correlate with height SDS of affected offspring (r = 0.24). For unaffected siblings as a group or analyzed separately as normals or carriers, there was a strong correlation between parental and offspring SDS for height (P < 0.01 for all comparisons). Thus, the effect of homozygosity for the GHR mutation was so profound as to abolish parental influence on height, and there was no difference in the influence of parental stature between carrier and noncarrier offspring. These findings demonstrate no meaningful effect on stature of heterozygosity for the E180 splice mutation of the GHR, which is a functional null mutation and, in the homozygous state, results in profound short stature from severe insulin-like growth factor-I deficiency.

Long-term glycemic control influences the onset of limited joint mobility in type 1 diabetes

BACKGROUND

Limited joint mobility (LJM) in childhood insulin-dependent (type 1) diabetes is associated with a substantially increased risk of microvascular complications. Cross-sectional studies have not demonstrated a relationship between LJM and metabolic control. This study was designed to determine whether glycemic control, as measured by glycohemoglobin (hgbA1C) levels from the onset of diabetes, is associated with the occurrence of LJM.

METHOD

Probands (n = 18) had hgbA1C values and recorded observation of joint function from soon after onset of their diabetes. Controls (n = 40) were matched to probands for gender and age at diagnosis and had follow-up beyond the age at which the proband was found to have LJM.

RESULTS

The odds ratio for occurrence of LJM for the mean hgbA1C from diabetes onset was 1.46, 95% confidence limits 1.07 to 2.00. Thus, for every unit increase in average hgbA1C, there was approximately a 46% increase in the risk of LJM. When hgbA1C was dichotomized, the OR for hgbA1C of more than 8% was 2.55, and the OR was 4.54 if the hgbA1C was greater than 12%. Age at diagnosis and duration of diabetes were not independent prognostic factors for LJM.

CONCLUSION

Glycemic control from onset of diabetes is strongly associated with occurrence of LJM.

Normal intelligence with severe insulin-like growth factor I deficiency due to growth hormone receptor deficiency: a controlled study in a genetically homogeneous population

Superior school performance was reported for 52 Ecuadorian probands with severe deficiency of insulin-like growth factor I (IGF-I) due to GH receptor deficiency (GHRD) resulting from homozygosity for the E180 splice mutation of the GHR. In contrast, subnormal intelligence was reported in a study of 18 genetically heterogeneous Israeli patients, attributed to frequent hypoglycemia or IGF-I dependence of brain development. This study is the first controlled evaluation of the intellectual ability of patients with GHRD. We compared the intelligence of 18 patients of school age (mean +/- SD age, 11.5 +/- 2.8 yr), 42 of their relatives (11.5 +/- 2.8 yr), and 28 community controls (10.0 +/- 0.8 yr), using a battery of intelligence tests that have been validated in cross-cultural research, designed to minimize the effects of physical size, motor coordination, and cultural background. Because all patients had the same GHR mutation, for which the carrier state could be determined, this study also investigated whether heterozygosity for mutation of the GHR among unaffected relatives is associated with intelligence. The intellectual ability of the patients with GHRD was not significantly different from that of their relatives (P > 0.05) on the psychometric tests of intelligence and was comparable to that of the community controls on the chronometric tests. Homozygosity or heterozygosity for the mutation in the GHR gene common to Ecuadorian patients was unrelated to intelligence (P > 0.05). These results indicate that the gene defect causing GHRD is not related to intelligence in the Ecuadorian population. They also indicate that GH-induced IGF-I production is not required for normal brain growth in utero or for postnatal intellectual development.

Bone mineral, histomorphometry, and body composition in adults with growth hormone receptor deficiency

Growth hormone (GH) and insulin-like growth factor I (IGF-I) deficiencies have been associated with osteopenia in both children and adults. To examine the effects of growth hormone resistance on bone mineral and body composition, we studied 11 adults (mean age 30 years) with growth hormone receptor deficiency (GHRD, Laron syndrome) and 11 age- and gender-matched controls from Southern Ecuador. Bone mineral and body composition were determined by dual-energy X-ray absorptiometry. Bone physiology was assessed with biochemical markers of bone turnover and dynamic bone histomorphometry. Bone size and body composition differed markedly between subjects with GHRD and controls. Affected adults were 40 cm shorter than controls, had significantly less lean body mass, and had increased percent body fat. Bone mineral content and density (BMD) at the spine, femoral neck, and whole body were significantly lower in adults with GHRD than in controls. Mean BMD Z scores were -1.5 to -1.6 at all sites in affected women and -2.2 to -2.3 in men with GHRD. Estimated volumetric bone density (BMAD) at the spine and femoral neck, however, was not reduced in GHRD. Spine BMAD was 0.210 +/- 0.025 versus 0.177 +/- 0.021 for affected women versus controls (p < 0.05) and 0.173 +/- 0.018 versus 0.191 +/- 0.025 for men with GHRD versus normals (p = 0.31). Urinary pyridinoline concentrations were significantly greater in adults with GHRD than in controls, while type I collagen C-telopeptide breakdown products and markers of bone formation did not differ. Differences in histomorphometry were limited to a reduction in trabecular connectivity; bone volume and formation rate were similar to controls. These data confirm the importance of the GH/IGF axis in regulating bone size and body composition. The contribution of these peptides to the acquisition and maintenance of bone mineral is less certain since volumetric bone density was preserved despite low levels of IGF-I and IGFBP-3 associated with GH resistance.

Non-insulin dependent diabetes mellitus (NIDDM) in minority youth: research priorities and needs

The prevalence of non-insulin dependent diabetes mellitus (NIDDM) is increasing in Native American and African-American youth, with females more frequently affected than males. This increase is related to increasing rates of obesity and to the greater demand for insulin at adolescence. This review examines the epidemiologic data about NIDDM in minority youth and addresses questions about the type of diabetes minority youth have, the relative contributions of environment and genetics to their diabetes, and whether prevention or control is possible. The heterogeneity of NIDDM in the minority youth population includes: typical NIDDM; atypical diabetes mellitus (ADM), which has been described in a substantial number of African-American youngsters; and a small proportion with a range of defects in the pathway of insulin action. Clinical and experimental evidence that insulin resistance or insulin deficiency is the primary defect in NIDDM are reviewed, as is evidence that fetal undernutrition may be a contributing factor. The numerous reports of linkages, associations, and mutations or polymorphisms in candidate genes account for a very small proportion of non-type 1 diabetes. Environmental and genetic contributors to obesity are also important. Research issues relating to the questions discussed include the need for data comparing various populations and assessing risk factors associated with the epidemic of NIDDM and obesity, costs to the health system and attendant personal and societal costs, clarification of the types of NIDDM in minority populations that will permit appropriate therapy and counseling, and extensive studies of environmental and genetic factors. Genetic studies include a genome wide search and continued analysis for candidate genes for both NIDDM and obesity. Environmental factors for study include the role of fetal and perinatal nutrition and drug exposure. Finally, collaborative multicenter studies are needed of prevention or control of obesity and NIDDM.

Effects of low level radiation from the Chernobyl accident in a population with iodine deficiency

To determine the effects of low dose radiation from 131I and 137Cs resulting from the Chernobyl disaster on the expression of endemic goiter in children, we studied children in regions with and without evidence of radiocontamination but comparable iodine insufficiency. We included 89 children in the study (radiocontaminated) region (SR) and 116 in the control region (CR) because they were either fetuses, infants, or pre-adolescents at the time of exposure. We evaluated thyroid dimensions by clinical examination and ultrasound; thyroid function by hormonal levels, and thyroglobulin measurement; histology of the thyroid by fine needle aspiration; and thyroid autoimmunity. SR subjects had 5 times the frequency of thyroid enlargement as those from CR, greatest in the younger patients. There were no instances of clinically apparent thyroid dysfunction. Antithyroid microsomal and antithyroglobulin antibodies were present in a markedly greater percentage of SR subjects. Fine needle biopsy demonstrated greater cellular proliferation in samples from SR.

CONCLUSIONS

We have demonstrated findings of autoimmune thyroid disease at markedly increased frequency in a population of children with poor iodine nutriture who were exposed to low level radiation, compared to a more iodine deficient population not so exposed. These results suggest that low level radiation may induce thyroid gland changes in children who have inadequate iodine intake nutriture and reinforce the importance of adequate dietary iodine.

Residential treatment for youngsters with difficult-to-manage insulin dependent diabetes mellitus

A descriptive outcome study of 52 children with insulin-dependent diabetes mellitus (IDDM) admitted to a residential treatment program over 6 years. Criteria for admission included repeated hospitalizations for diabetes-related problems, excessive school absences, and/or familial disruption. Residential treatment included individual, group, and family psychotherapy, diabetes education, and close medical supervision. The design included collection of data before, during and after treatment. Children admitted to the residential unit were compared to a population of pediatric IDDM outpatients from the same geographical area. Treatment was associated with a reduction in diabetes-related hospitalizations, improved school attendance, decreased glycosylated hemoglobin levels, weight gain, individualized insulin changes, improved knowledge about diabetes, and a normalization of attitudes towards this disease.

Growth hormone insensitivity

Growth hormone insensitivity (GHI) may be primary, caused by defects in the GH receptor, or further along the GH-insulin-like growth factor-I (IGF-I) axis, or secondary, resulting from a variety of illnesses or malnutrition affecting various steps in the pathway from the GH binding to IGF-I action. GH receptor deficiency, although rare, with only 229 cases reported, is the most common cause of primary GHI. Most patients are of Jewish, Arab, or other Mediterranean origin, the largest cohort being Catholics of Jewish origin coming from a small area in southern Ecuador, who account for one third of known cases. This large cohort has provided insight into the clinical features, growth characteristics, biochemical features, and effects of treatment with recombinant IGF-I. The Ecuadorian patients share a splice site mutation in the GH receptor gene with at least one Israeli patient of Iberian origin; 27 other mutations and a major deletion have been described in other affected patients.

Two-year treatment of growth hormone (GH) receptor deficiency with recombinant insulin-like growth factor I in 22 children: comparison of two dosage levels and to GH-treated GH deficiency

We have reported 1-yr results of a double blind, placebo-controlled trial of recombinant human insulin-like growth factor I (rhIGF-I) replacement in 16 children from the Ecuadorian GH receptor-deficient (GHRD) population. This report extends observations of rhIGF-I efficacy at two dosage levels [120 micrograms/kg BW twice daily (n = 15) and 80 micrograms/kg twice daily (n = 7)] over 2 yr, compares biochemical responses [serum IGF-I and IGF-binding protein-3 (IGFBP-3)] and their relationship to growth effects, and compares treatment effects of rhIGF-I in GHRD to rhGH in idiopathic GH deficiency (GHD). There were no baseline differences between the low and high dose groups for growth velocity (GV), bone age (BA), SD score for height, or percent mean body weight for height (MBWH). Over 2 yr of rhIGF-I treatment, there were no differences in GV or in changes in height SD score, height age (HA), or BA between the two groups; a subgroup of six subjects at the higher dose followed for a third year continued at the second year GV. The higher dose resulted in a greater change in percent MBWH. GV in yr 1 and 2 for the entire group and in yr 3 for a subgroup were greater for GH-treated GHD (n = 11). The GHD group showed a greater change in SD score for height and HA, but did not differ from the rhIGF-I-treated GHRD group in the change in BA (delta BA) or delta HA/delta BA over 2 yr. There was a greater change in percent MBWH in GHRD. There were no differences between dosage groups for serum IGF-I levels at baseline or the near-normal trough levels 12 h after rhIGF-I injection; these individual levels correlated with HA gain in yr 1 and 2. IGFBP-3 levels were markedly low, with no changes of significance with treatment. Comparable growth responses to the two dosage levels and the biochemical changes indicate a plateau effect at or below 80 micrograms/kg BW twice daily. The growth response and favorable trough levels of IGF-I despite the overall lack of increase in circulating IGFBP-3 levels suggest an alternative mechanism for sustaining IGF-I levels and avoiding rapid clearance of rhIGF-I. The greater increase in MBWH with treatment of GHRD than with treatment of GHD may reflect comparable effects on lean body mass without the lipolytic effects of GH in the GHRD subjects. The difference in growth response between rhIGF-I-treated GHRD and rhGH-treated GHD groups is consistent with the hypothesis that 20% or more of GH-influenced growth is due to the direct effects of GH on bone. Nonetheless, the comparable delta HA/delta BA suggests similar long term effects of replacement therapy in the two conditions.

Connective tissue and joint disease in diabetes mellitus

Connective tissue is ubiquitous and subject to alterations that result in changes in the extracellular matrix of vessels and tissues leading to the long-term complications of diabetes. This article reviews only those abnormalities of interstitial connective tissue involving skeleton, joints, skin, and periarticular tissues. Abnormalities in the skin and periarticular tissues result in syndromes limiting joint movement, including limited joint mobility, Dupuytren disease, flexor tenosynovitis, carpal tunnel syndrome, stiff-hand syndrome, and shoulder-hand reflex dystrophy. Of these, only limited joint mobility and stiff-hand syndrome occur exclusively in patients with diabetes. In all of these conditions, advanced glycation end products are thought to form as a result of nonenzymatic reaction of glucose with proteins, causing stiffening.

Diabetic ketoacidosis (DKA): treatment guidelines

Diabetic ketoacidosis (DKA), resulting from severe insulin deficiency, accounts for most hospitalization and is the most common cause of death, mostly due to cerebral edema, in pediatric diabetes. This article provides guidelines on management to restore perfusion, stop ongoing ketogenesis, correct electrolyte losses, and avoid hypokalemia and hypoglycemia and the circumstances that may contribute, in some instances, to cerebral edema (overhydration, rapid osmolar shifts, hypoxia). These guidelines emphasize the importance of monitoring glycemia, electrolytes, hydration, vital signs, and neurologic status in a setting where response can be rapid if necessary (e.g., mannitol for cerebral edema). Most important is the prevention of DKA in established patients by close supervision of those most likely to omit insulin, or during illness, and a high index of suspicion for diabetes to prevent deterioration to DKA in new patients, particularly those under age 5, who are at greatest risk of complications.

Growth hormone receptor deficiency (Laron syndrome) in black African siblings

Non-Caucasians with growth hormone receptor (GHR) deficiency/Laron syndrome among the approximately 180 recognised cases are rare, and include a Japanese and 3 African Americans. Black African siblings, a brother and a sister seen initially at 11 years 9 months and 5 years 6 months of age respectively were -7,4 and -8,0 on the standard deviation score for height. They had characteristic features and biochemical findings including prominent forehead; depressed nasal bridge; central adiposity; high-pitched voices; micropenis; high GH levels and low levels of insulin-like growth factor (IGF)-I, IGF-II, insulin-like growth factor-binding protein 3 (IGFBP-3), and GH-binding protein (the solubilised extracellular domain of the GH cell surface receptor). Molecular genetic studies revealed a dinucleotide deletion in both siblings on exon 7 of the GHR gene, a mutation not found in any other GHR-deficient patient studied, including the North Americans of African origin. Since African Americans have a substantial admixture of Caucasian genes, it is of interest to document the presence of this condition in siblings from Africa.

Severe growth hormone insensitivity (Laron syndrome) due to nonsense mutation of the GH receptor in brothers from Russia

Primary GH insensitivity (Laron syndrome) due to GH receptor deficiency (GHRD) is an autosomal recessive condition characterized by severe growth failure. Diverse alterations in the GHR gene have been reported in affected individuals. We report here the first family with GHRD from Russia, with two affected siblings and consanguineous parents. Analysis of blood spot DNA by polymerase chain reaction (PCR), denaturing gradiant gel electrophoresis, and nucleotide sequencing indicated that these siblings are homozygous for a nonsense mutation, R43X, in the GHR gene. The R43X mutation, which changes an arginine codon to a translational stop codon, occurs at a CpG dinucleotide mutational hotspot and has previously been identified in affected individuals of Mediterranean and Ecuadorian origin.

Long-term effects of insulin-like growth factor (IGF)-I treatment on serum IGFs and IGF binding proteins in adolescent patients with growth hormone receptor deficiency

OBJECTIVE

The aim of this investigation was to study the effect of relatively high dose IGF-I therapy given for several months, on serum levels of IGF-I, IGF-II and IGFBP-3, and on IGF-I pharmacokinetics in patients with growth hormone insensitivity due to GH receptor dysfunction.

DESIGN AND PATIENTS

Two adolescent subjects from Ecuador were treated with recombinant IGF-I at a dosage of 120 micrograms/kg s.c. twice daily, in combination with a GnRH analogue for 8 months.

MEASUREMENTS

Serum was sampled at baseline and at 3-8 months, for determination of IGF-I, IGF-II and IGFBP-3 by radioimmunoassay, and for evaluation of IGFBPs and IGFBP-3 protease activity by Western ligand blot and protease assay, respectively.

RESULTS

Peak serum IGF-I levels ranged from 272 to 492 micrograms/l. Mean serum IGF-II levels were decreased concurrently with the increase in IGF-I. Serum IGFBP-3 levels failed to rise with prolonged IGF-I treatment. There was no apparent change in the half-life of IGF-I during the treatment period.

CONCLUSIONS

IGF-I administration does not increase serum levels of IGFBP-3 or significantly alter IGF-I pharmacokinetics.

A randomized, double blind, placebo-controlled trial on safety and efficacy of recombinant human insulin-like growth factor-I in children with growth hormone receptor deficiency

GH insensitivity due to GH receptor deficiency is a rare autosomal recessive condition, characterized by deletions or mutations of the GH receptor gene. Patients are refractory to both endogenous and exogenous GH, resulting in severe growth retardation. Therapy with recombinant human insulin-like growth factor-I (rhIGF-I) can bypass the defect in the GH receptor and potentially stimulate growth. We previously identified a genetically homogeneous group of patients in southern Ecuador, thus providing a patient base for a controlled clinical trial of rhIGF-I therapy. Seventeen prepubertal patients were entered in a randomized, double blind, placebo-controlled trial. Subjects received either a 12-month course of rhIGF-I (120 micrograms/kg, sc, daily) or 6 months of placebo followed by 6 months of rhIGF-I. Subjects receiving rhIGF-I showed a significant increase in growth rate, which was sustained over the 1-yr course of therapy (from 2.9 +/- 0.6 to 8.6 +/- 0.4 cm/yr). Incidents of hypoglycemia were equal in frequency in the placebo and rhIGF-I groups. One recipient of rhIGF-I developed papilledema, which resolved spontaneously. rhIGF-I therapy did not alter serum IGF-binding protein-3 concentrations. rhIGF-I treatment is effective in stimulating skeletal growth in GH receptor deficiency. Although the therapy proved to be safe, the potent metabolic actions of rhIGF-I and the persistently low levels of serum IGF carrier protein necessitate continued careful observation for side-effects.

Growth in growth hormone insensitivity

Primary GH insensitivity due to GH receptor deficiency (GHRD) provides a model for studying the discrete effects of severe IGF-I deficiency on growth and body composition. Growth failure in utero is doubtful, but postpartum growth proceeds at rates that result in adult statures 4-12 standard deviations (SDs) below the normal mean. Wide variability in statural effect, even in a genetically homogeneous population, is partly explained by correlation of SD score with biochemical measures of GH effect (IGF-I, IGF-II, and IGFBP-3). Growth and changes in body composition (decreased fat/lean) in patients with GHRD in response to exogenous IGF-I indicate that direct local effects of GH are not necessary for these responses.

Facial morphometry of Ecuadorian patients with growth hormone receptor deficiency/Laron syndrome

Facial morphometry using computerised image analysis was performed on patients with growth hormone receptor deficiency (Laron syndrome) from an inbred population of southern Ecuador. Morphometrics were compared for 49 patients, 70 unaffected relatives, and 14 unrelated persons. Patients with growth hormone receptor deficiency showed significant decreases in measures of vertical facial growth as compared to unaffected relatives and unrelated persons with short stature from other causes. This report validates and quantifies the clinical impression of foreshortened facies in growth hormone receptor deficiency.

Growth hormone (GH) insensitivity due to primary GH receptor deficiency

As demonstrated in Table 2, the differential diagnosis of growth hormone insensitivity (GHI) includes a number of discrete disorders that can be broadly classified as primary or secondary forms. We have selected GHRD (Laron syndrome) as the prototypic disorder of GHI, in part because such dramatic and rapid progress has been made in this clinical condition over the last 6 yr. These advances represent the fortunate convergence of: 1) the cloning of the GHR gene and the identification of deletions and mutations of this gene in GHRD; 2) the development of assay methods for measurement of the GHBP, IGF peptides, and binding proteins; 3) the discovery of a larger number of affected individuals than had been previously suspected, including the recognition and description of a large genetically homogeneous population of GHRD patients in Ecuador; and 4) the production of recombinant IGF-I for therapeutic trials in GHRD. Although we are still in the early phases of clinical trials of recombinant hIGF-I in GHRD, preliminary results have been encouraging. Whether this promise translates into genuine improvements in height and body composition, without significant clinical toxicity, remains to be determined. Similarly, the suitability of IGF-I therapy for other, particularly secondary, forms of GHI is still uncertain, although the responsiveness of GHD-IA patients seems to parallel that seen in GHRD (66, 78). The next few years should provide exciting and potentially important new data on the clinical spectrum, biochemical and molecular characteristics, and responsiveness to therapy of syndromes of GHI.