Mutations in pregnancy-associated plasma protein A2 cause short stature due to low IGF-I availability.

Mutations in multiple genes of the growth hormone/IGF-I axis have been identified in syndromes marked by growth failure. However, no pathogenic human mutations have been reported in the six high-affinity IGF-binding proteins (IGFBPs) or their regulators, such as the metalloproteinase pregnancy-associated plasma protein A2 (PAPP-A2) that is hypothesized to increase IGF-I bioactivity by specific proteolytic cleavage of IGFBP-3 and -5. Multiple members of two unrelated families presented with progressive growth failure, moderate microcephaly, thin long bones, mildly decreased bone density and elevated circulating total IGF-I, IGFBP-3, and -5, acid labile subunit, and IGF-II concentrations. Two different homozygous mutations in PAPPA2, p.D643fs25* and p.Ala1033Val, were associated with this novel syndrome of growth failure. In vitro analysis of IGFBP cleavage demonstrated that both mutations cause a complete absence of PAPP-A2 proteolytic activity. Size-exclusion chromatography showed a significant increase in IGF-I bound in its ternary complex. Free IGF-I concentrations were decreased. These patients provide important insights into the regulation of longitudinal growth in humans, documenting the critical role of PAPP-A2 in releasing IGF-I from its BPs.

Celiac disease in children, adolescents, and young adults with autoimmune thyroid disease.

OBJECTIVE: To determine the prevalence of antibodies associated with celiac disease and biopsy-proven celiac disease in children with autoimmune thyroid disease. STUDY DESIGN: A total of 302 patients with positive anti-thyroid antibodies were prospectively studied. Total immunoglobulin A (IgA) and tissue transglutaminase-IgA (tTG-IgA) levels were obtained. Those with a positive tTG-IgA titer were offered biopsy for definitive diagnosis of celiac disease. RESULTS: A total of 4.6% of subjects with autoimmune thyroid disease had positive tTG-IgA titers. The prevalence of biopsy-confirmed celiac disease was 2.3%. Our population was enriched with patients with type 1 diabetes mellitus (4.3%) and Down syndrome (3.4%). Excluding individuals with these co-morbidities, the prevalence of celiac disease in autoimmune thyroid disease is 1.3%, similar to that of the general population. The positive predictive value of biopsy-proven celiac disease in patients with autoimmune thyroid disease and positive tTG-IgA titer was 54%. CONCLUSION: The increase in prevalence of celiac disease in autoimmune thyroid disease in our study was largely caused by enrichment with co-morbidities. Without comorbidities or symptoms, screening for celiac disease may not be justified in this population. The specificity of tTG-IgA titer for the diagnosis of celiac disease was decreased in patients with autoimmune thyroid disease compared with the general population.

The effect of oral leucine on protein metabolism in adolescents with type 1 diabetes mellitus.

Lack of insulin results in a catabolic state in subjects with insulin-dependent diabetes mellitus which is reversed by insulin treatment. Amino acid supply, especially branched chain amino acids such as leucine, enhances protein synthesis in both animal and human studies. This small study was undertaken to assess the acute effect of supplemental leucine on protein metabolism in adolescents with type 1 diabetes. L-[1-(13)C] Leucine was used to assess whole-body protein metabolism in six adolescent females (16-18 yrs) with type 1 diabetes during consumption of a basal diet (containing 58 µmoles leucine/kg/h) and the basal diet with supplemental leucine (232 µmoles leucine/kg/h). Net leucine balance was significantly higher with supplemental leucine (56.33 ± 12.13 µmoles leucine/kg body weight/hr) than with the basal diet (-11.7 ± -5.91, P < .001) due to reduced protein degradation (49.54 ± 18.80 µmoles leucine/kg body weight/hr) compared to the basal diet (109 ± 13.05, P < .001).

Does pituitary stalk function improve with age?

Ectopic posterior pituitary hyperintensity on MRI is a common feature associated with growth hormone deficiency. The presence of at least some residual components of the pituitary stalk is necessary for adequate anterior pituitary function. Little is known about long-term change in pituitary function or MRI findings in patients with ectopic posterior pituitary and interrupted pituitary stalk. We describe a case of childhood growth hormone deficiency and hyperprolactinemia associated with absent pituitary stalk. As an adult, prolactin levels normalized and GH secretion improved associated with changes in MRI findings.

Effect of insulin with oral nutrients on whole-body protein metabolism in growing pubertal children with type 1 diabetes.

Insulin treatment of children with insulin-dependent diabetes mellitus improves whole body protein balance. Our recent study, conducted in pubertal children with type 1 diabetes with provision of both insulin and amino acids, indicated a positive effect of insulin on protein balance, primarily through decreased protein degradation. The current study was undertaken to assess the effect of insulin on protein metabolism in adolescents with type 1 diabetes during oral provision of a complete diet. Whole-body protein metabolism in six pubertal children (13-17 y) with type 1 diabetes mellitus was assessed with L-[1-13C]leucine during a basal (insulin-withdrawn) period and during infusion of 0.15 U/kg/h regular insulin with hourly meals to meet protein and energy requirements. Net leucine balance was significantly higher with insulin and nutrients (13.1 +/- 6.3 micromol leucine/kg/h) than in the basal state (-21.4 +/- 2.8, p < 0.01) with protein degradation decreased from 138 +/- 5.6 mumol leucine/kg/h to 108 +/- 5.9 (p < 0.01) and no significant change in protein synthesis. Even with an ample supply of nutrients, insulin does not increase whole-body protein synthesis in pubertal children with type 1 diabetes mellitus and positive protein balance is solely due to a substantial reduction in the rate at which protein is degraded.