Gabriela Sobrero

Congenital goitrous hypothyroidism: mutation analysis in the thyroid peroxidase gene

Background  Iodide organification defect (IOD) is characterized by a reduced ability of the thyroid gland to retain iodide resulting in hypothyroidism. Mutations in thyroid peroxidase (TPO) gene appear to be the most common cause of IOD and are commonly inherited in an autosomal recessive fashion. The TPO gene is located on the chromosome 2p25. It comprises 17 exons, covers approximately 150 kb of genomic DNA and codes 933 amino acids.

Serum levels of adiponectin and leptin in children born small for gestational age: relation to insulin sensitivity parameters.

ABSTRACT Children born small for gestational age (SGA) are prone to developing obesity, insulin resistance and type 2 diabetes. Adiponectin and leptin are adipocytokines associated with insulin sensitivity parameters. We aimed to relate serum adiponectin and leptin levels with insulin sensitivity parameters in prepuberal SGA children with and without catch-up growth (SGA+CUG; SGA-CUG, respectively) and to analyze the usefulness of these adipocytokines as early markers of insulin resistance. We analysed adiponectin, proinsulin, leptin, growth factors, insulin, HOMA IR and HOMA βcell in 23 SGA+CUG, 26 SGA-CUG children compared with 48 prepuberal appropiate for gestational age (AGA). SGA children had adiponectin levels comparable to AGA children. Leptin levels were different between sexes, showed to be higher in SGA+CUG group (p=0.040) and these were significantly correlated with insulin sensitivity parameters. These results suggest leptin resistance as an adaptive mechanism to increase energy balance, but an altered functional response of adipocytes cannot be discarded.

New insights into thyroglobulin gene: Molecular analysis of seven novel mutations associated with goiter and hypothyroidism

The thyroglobulin (TG) gene is organized in 48 exons, spanning over 270 kb on human chromosome 8q24. Up to now, 62 inactivating mutations in the TG gene have been identified in patients with congenital goiter and endemic or non-endemic simple goiter. The purpose of the present study was to identify and characterize new mutations in the TG gene. We report 13 patients from seven unrelated families with goiter, hypothyroidism and low levels of serum TG. All patients underwent clinical, biochemical and imaging evaluation. Single-strand conformation polymorphism (SSCP) analysis, endonuclease restriction analysis, sequencing of DNA, genotyping, population screening, and bioinformatics studies were performed. Molecular analyses revealed seven novel inactivating TG mutations: c.378C>A [p.Y107X], c.2359C>T [p.R768X], c.2736delG [p.R893fsX946], c.3842G>A [p.C1262Y], c.5466delA [p.K1803fsX1833], c.6000C>G [p.C1981W] and c.6605C>G [p.P2183R] and three previously reported mutations: c.886C>T [p.R277X], c.6701C>A [p.A2215D] and c.7006C>T [p.R2317X]. Six patients from two families were homozygous for p.R277X mutation, four were compound heterozygous mutations (p.Y107X/p.C1262Y, p.R893fsX946/p.A2215D, p.K1803fsX1832/p.R2317X), one carried three identified mutations (p.R277X/p.C1981W-p.P2183R) together with a hypothetical micro deletion and the remaining two siblings from another family with typical phenotype had a single p.R768X mutated allele. In conclusion, our results confirm the genetic heterogeneity of TG defects and the pathophysiological importance of altered TG folding as a consequency of truncated TG proteins and missense mutations located in ACHE-like domain or that replace cysteine.

Vitamin D receptor genotypes are associated with bone mass in patients with Turner syndrome.

Abstract Background: Turner syndrome (TS) patients present low bone mineral density (BMD) and increased fracture risk, probably due to a genetic defect aggravated by hormonal deficiency. Aim: To study the relationship between vitamin D receptor (VDR) gene polymorphisms and BMD and bone parameters in TS patients. Methods: DNA from 65 TS patients and 110 controls was amplified by PCR and digested with Fok I, Bsm I and Apa I restrictases. Lumbar and femoral BMD were determined by DEXA and serum intact parathyroid hormone, osteocalcin and β-CrossLaps by electrochemiluminescence. Results: Genotype distribution within the Apa I site was different in both groups: genotype Aa was more abundant in TS (63.8% vs. 41.3%; p<0.01), whereas AA predominated in controls (33.9% vs. 15.5%; p<0.01). Patients carrying genotype bb (Bsm I) or ff (Fok I) had lower BMD than those with other genotypes (p<0.01 and p<0.05, respectively). Conclusion: Bsm I and Fok I polymorphic sites of VDR could be genetic determinants of BMD in TS patients.

Association of vitamin D receptor gene Cdx2 polymorphism with bone markers in Turner syndrome patients.

Abstract Background: Turner syndrome (TS) patients usually have low bone mineral density (BMD) and increased risk of osteoporotic fractures. We have previously demonstrated an association of bb (BsmI polymorphic site) and ff (FokI polymorphic site) vitamin D receptor (VDR) genotypes with reduced BMD in TS patients. Aim: To analyze the relationship between VDR-Cdx2 polymorphism and BMD as well as bone metabolic variables in TS patients. Methods: Fifty-five TS patients and 59 control women were studied. VDR-Cdx2 genotypes were determined using TaqMan probes in a real time thermocycler. Lumbar and femoral BMD were determined by dual-energy X-ray absorptiometry (DEXA) and serum intact parathyroid hormone, osteocalcin and β-CrossLaps were determined by electrochemiluminescence. Results: Patients with genotype GG had higher levels of both osteocalcin and β-CrossLaps as compared to patients with genotype GA (p<0.01 and p<0.05, respectively). Conclusion: Patients carrying genotype GG have higher levels of bone formation and resorption markers. This indicates a more active bone turnover that could impact on their future bone mineral density.

Growth hormone (GH) treatment reduces peripheral thyroid hormone action in girls with Turner syndrome

Objective  Turner syndrome (TS) is an indication for GH therapy in spite of the modest growth response. Somatic growth depends not only on GH insulin‐like growth factor I (IGF‐I) axis but also on thyroid hormone (TH) status. We have previously reported that supraphysiological IGF‐I levels diminished TH actions in rat tissues by reducing the nuclear TH receptor (TR). GH treatment to TS patients induces high IGF‐I levels and therefore a reduction of TH action in tissues may be expected. We aimed at evaluating the effect of GH therapy in TS girls on peripheral TH action.

Clinical and molecular studies related to bone metabolism in patients with congenital adrenal hyperplasia

Abstract Patients with congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency need glucocorticoid (GC) therapy, which alters bone mineral metabolism. We analyze clinical and biochemical parameters and different polymorphisms of candidate genes associated with bone mineral density (BMD) in CAH patients. The CAH patients treated with GC and healthy controls were studied. Anthropometric parameters, biochemical markers of bone turnover, and BMD were evaluated. Polymerase chain reaction technique was used to genotype different candidate genes. The 192-192 genotype frequency (IGF-I) was lower in poorly controlled patients than that from controls. In CAH patients, FF genotype (vitamin D receptor, VDR) correlated with lower lumbar spine BMD and there was a significant association between the 0-0 genotype (IGF-I) and high values of β-CrossLaps and a low total BMD. This study contributes to understanding of the association of genetic determinants of BMD with the variable response to GC treatment in CAH patients and demonstrates the usefulness of these genetic polymorphisms.