Carlos Alberto Longui

Central Precocious Puberty Caused by Mutations in the Imprinted Gene MKRN3

BACKGROUND The onset of puberty is first detected as an increase in pulsatile secretion of gonadotropin-releasing hormone (GnRH). Early activation of the hypothalamic-pituitary-gonadal axis results in central precocious puberty. The timing of pubertal development is driven in part by genetic factors, but only a few, rare molecular defects associated with central precocious puberty have been identified. METHODS We performed whole-exome sequencing in 40 members of 15 families with central precocious puberty. Candidate variants were confirmed with Sanger sequencing. We also performed quantitative real-time polymerase-chain-reaction assays to determine levels of messenger RNA (mRNA) in the hypothalami of mice at different ages. RESULTS We identified four novel heterozygous mutations in MKRN3, the gene encoding makorin RING-finger protein 3, in 5 of the 15 families; both sexes were affected. The mutations included three frameshift mutations, predicted to encode truncated proteins, and one missense mutation, predicted to disrupt protein function. MKRN3 is a paternally expressed, imprinted gene located in the Prader-Willi syndrome critical region (chromosome 15q11-q13). All affected persons inherited the mutations from their fathers, a finding that indicates perfect segregation with the mode of inheritance expected for an imprinted gene. Levels of Mkrn3 mRNA were high in the arcuate nucleus of prepubertal mice, decreased immediately before puberty, and remained low after puberty. CONCLUSIONS Deficiency of MKRN3 causes central precocious puberty in humans. (Funded by the National Institutes of Health and others.).

Glucocorticoid therapy: minimizing side effects

OBJECTIVE To describe the main undesirable side effects of glucocorticoid therapy, mechanisms of action and the necessary measures to minimize side effects. SOURCES Authors experience, supplemented with papers published in MEDLINE. SUMMARY OF THE FINDINGS The principles for minimizing undesirable side effects of glucocorticoid therapy include: a) only use glucocorticoids if they are essential; b) avoid the use of long-acting glucocorticoids, using short- and intermediate-acting glucocorticoids instead; c) keep treatment as short as possible, since treatment lasting 5 to 7 days shows fewer side effects and quick recovery of the hypothalamic-pituitary axis; d) use glucocorticoids with local activity preferentially, such as inhaled glucocorticoids; e) use in association with other drugs, especially with other more specific anti-inflammatory or immune suppressive drugs, promoting a synergistic effect in order to avoid the use of glucocorticoids or to reduce dosage and duration of glucocorticoid therapy; f) indicate the minimum effective dose, respecting individual sensitivity to glucocorticoids. CONCLUSION In order to choose the best glucocorticoid schedule it is essential to understand the pharmacological characteristics and the biological action of glucocorticoids, allowing the most adequate indication, glucocorticoid dose, mode of administration and the duration of glucocorticoid therapy.

Low Frequency of CYP21B Deletions in Brazilian Patients with Congenital Adrenal Hyperplasia Due to 21-Hydroxylase Deficiency

The frequency of large mutations was determined in 131 Brazilian patients with different clinical forms of 21-hydroxylase deficiency, belonging to 116 families. DNA samples were examined by Southern blotting hybridization with genomic CYP21 and C4cDNA probes after TaqI and BglII restriction. Large gene conversions were found in 6.6% and CYP21B deletions in 4.4% of the alleles. The breakpoint in these hybrid genes occurred after exon 3 in 92% of the alleles. All rearrangements involving CYP21B gene occurred in the heterozygous form, except in a patient with simple virilizing form who presented homozygous CYP21B deletion. Our data showed that in these Brazilian patients, CYP21B deletions were less frequent than in most of the large series previously reported.

The degree of external genitalia virilization in girls with 21-hydroxylase deficiency appears to be influenced by the CAG repeats in the androgen receptor gene

Background  Women with 21‐hydroxylase deficiency present much variability in external genitalia virilization, even among those with similar impairments of 21‐hydroxylase (21OH) activity.

Corticoterapia: minimizando efeitos colaterais

OBJECTIVE:To describe the main undesirable side effects of glucocorticoid therapy, mechanisms of action and the necessary measures to minimize side effects. SOURCES: Authors experience, supplemented with papers published in MEDLINE. SUMMARY OF THE FINDINGS: The principles for minimizing undesirable side effects of glucocorticoid therapy include: a) only use glucocorticoids if they are essential; b) avoid the use of long-acting glucocorticoids, using short- and intermediate-acting glucocorticoids instead; c) keep treatment as short as possible, since treatment lasting 5 to 7 days shows fewer side effects and quick recovery of the hypothalamic-pituitary axis; d) use glucocorticoids with local activity preferentially, such as inhaled glucocorticoids; e) use in association with other drugs, especially with other more specific anti-inflammatory or immune suppressive drugs, promoting a synergistic effect in order to avoid the use of glucocorticoids or to reduce dosage and duration of glucocorticoid therapy; f) indicate the minimum effective dose, respecting individual sensitivity to glucocorticoids. CONCLUSION: In order to choose the best glucocorticoid schedule it is essential to understand the pharmacological characteristics and the biological action of glucocorticoids, allowing the most adequate indication, glucocorticoid dose, mode of administration and the duration of glucocorticoid therapy.

Prolonged Physical Training Decreases mRNA Levels of Glucocorticoid Receptor and Inflammatory Genes

Background/Aims: Prolonged physical exercise induces adaptive alterations in the hypothalamic-pituitary axis, increasing cortisol metabolism, and reducing cortisol synthesis and glucocorticoid sensitivity. The mechanisms responsible for this relative glucocorticoid resistance remain unknown but may involve expression of genes encoding glucocorticoid receptor (GR) and/or inflammatory molecules of nuclear factor kappa B1 (NFkB1) signaling pathway and cytokines. This study aimed to determine the impact of prolonged physical training on the expression of genes involved in glucocorticoid action and inflammatory response. Methods: Normal sedentary male cadets of the Brazilian Air Force Academy were submitted to 6 weeks of standardized physical training. Eighteen of 29 initially selected cadets were able to fully complete the training program. Fasting glucose, insulin and cortisol levels, cytokine concentration and the expression of genes encoding GR, NFkB1, inhibitor of NFkB1 and IkB kinase A were determined before and after the training period. Results: Prolonged physical exercise reduced the basal cortisol levels and the percent cortisol reduction after dexamethasone. These findings were associated with a significant reduction in the mRNA levels of GR (6.3%), NFkB1 (63%), inhibitor of NFkB1 (25%) and IkB kinase A (46%) with concomitant reduction in cytokine concentrations (ELISA). Conclusions: Prolonged physical training decreases the glucocorticoid sensitivity and the mRNA levels of the GR gene combined with decreased mRNA of genes related to the NFkB pathway.

Serum inhibin levels before and after gonadotropin stimulation in cryptorchid boys under age 4 years.

We evaluated eleven cryptorchid boys under four years of age to determine the usefulness of serum inhibin as a marker of seminiferous tubule dysfunction. Serum testosterone, inhibin, LH and FSH concentrations were measured by RIA before and after 6 weeks of human chorionic gonadotropin plus human menopausal gonadotropin therapy, and bilateral testicular biopsies were performed at orchiopexy. Hormonal results from the cryptorchid group were compared to those from an age-matched control group. Basal LH and testosterone levels were similar in the two groups. Cryptorchid boys had lower basal inhibin and higher FSH levels than controls. After gonadotropin treatment the inhibin/FSH ratio was lower in cryptorchid than control children, suggesting the presence of seminiferous tubule damage (p = 0.002). Normal numbers of spermatogonia were seen in 6/9 scrotal and in 1/13 cryptorchid testes. The peak of inhibin was positively correlated to the number of spermatogonia (r = 0.68; p = 0.02). We conclude that basal and stimulated inhibin concentrations, as well as basal and stimulated inhibin/FSH ratio, provide additional information on seminiferous tubule function in cryptorchid boys and can be useful to evaluate Sertoli cell function in these patients.

Lack of association between optineurin gene variants T34T, E50K, M98K, 691_692insAG and R545Q and primary open angle glaucoma in Brazilian patients.

Purpose: To verify the frequencies of T34T, E50K, M98K, 691_692insAG, and R545Q variants in the optineurin (OPTN) gene in Brazilian subjects with primary open-angle glaucoma (POAG) and controls. Patients and Methods: Ninety-nine patients with POAG and 100 normal controls were enrolled in this study. The frequency of alterations in the OPTN gene was analyzed by direct sequencing and enzymatic digestion of PCR products. Results: None of the five alterations evaluated was significantly associated with POAG when compared to controls. However, the T34T silent change was present in greater frequency in POAG patients (37.37% vs. 23.00% in controls), while the R545Q change was more prevalent in controls (23.00% vs. 10.10% in POAG). The M98K and 691_692insAG presented with low frequencies in POAG patients (1.01% and 2.02%, respectively) and controls (2.00% and 2.00%, respectively). The E50K substitution was not observed. Conclusion: Our data show no association between the five evaluated variants and POAG in the Brazilian population.

Aspectos moleculares da sensibilidade aos glicocorticóides

Glucocorticoids play an essential role in maintaining basal and stress-related homeostasis. Most known effects of glucocorticoids are mediated by the intracellular glucocorticoid receptors. The glucocorticoid sensitivity seems to depend on the amount of receptors expressed and the efficiency of glucocorticoid receptor-mediated signal transduction. Glucocorticoid resistance or hypersensitivity, seen in autoimmune-inflammatory diseases and in metabolic syndrome respectively, can represent the variability of several steps that influence the signaling cascade of glucocorticoid action. The recognition of these steps could provide the understanding of the clinical phenotype and course of such diseases as well as their responsiveness to glucocorticoid therapy. The comprehension of these pathophysiological mechanisms can also improve the possible therapeutic interventions. In this review, we have summarized the multiple factors that have been shown to be involved in this signaling cascade and, thus, to influence glucocorticoid sensitivity.

Evaluation of the hypothalamic-pituitary-thyroid axis in children with Down syndrome

OBJECTIVE To determine the thyroid stimulating hormone (TSH) secretion in children with Down syndrome (DS), who do not present clinical and laboratory evidence of classical hypothyroidism and concomitant undetectable antibodies. METHODS Fourteen children with DS with a mean age of 3.4 (+/- 1.8) years were studied. Patients with classical hypothyroidism or hyperthyroidism or those with positive antithyroid antibodies were excluded. The DS group was compared to a control group of 16 children with a mean age of 11.8 (+/- 3.8) years, diagnosed as having familial short stature or constitutional growth delay. Both groups underwent hormonal measurements at basal condition to determine serum TSH, T3, T4, free T4 and prolactin concentrations and after stimulation with thyrotropin releasing hormone (TRH). Thyroid hormones concentrations were also compared when children with DS were subdivided into two groups according to their basal TSH levels. RESULTS Basal TSH and prolactin levels were significantly higher in DS group. After stimulation with TRH, TSH peak was higher in the DS group. The number of patients presenting basal TSH levels higher than 5 microU/mL and TSH peaks higher than 30 microU/mL were significantly higher in the DS group. CONCLUSIONS Children with Down syndrome present frequent increase in basal TSH concentrations, despite the presence of normal basal thyroid hormones levels and negative antithyroid antibodies. Most of them (65%) show early intense response after TRH stimulation. Our data demonstrate that in spite of the absence of classic hypothyroidism and/or antithyroid antibodies, an abnormal pattern of TSH secretion occurred in patients with Down syndrome, possibly related to hypothalamic dysfunction.