VINICIUS NAHIME DE BRITO
Projetos de Pesquisa
Unidades Organizacionais
LIM/42 - Laboratório de Hormônios e Genética Molecular, Hospital das Clínicas, Faculdade de Medicina
5 resultados
Resultados de Busca
Agora exibindo 1 - 5 de 5
- The Congenital and Acquired Mechanisms Implicated in the Etiology of Central Precocious Puberty(2023) BRITO, Vinicius N.; CANTON, Ana P. M.; SERAPHIM, Carlos Eduardo; ABREU, Ana Paula; MACEDO, Delanie B.; MENDONCA, Berenice B.; KAISER, Ursula B.; ARGENTE, Jesus; LATRONICO, Ana ClaudiaThe etiology of central precocious puberty (CPP) is multiple and heterogeneous, including congenital and acquired causes that can be associated with structural or functional brain alterations. All causes of CPP culminate in the premature pulsatile secretion of hypothalamic GnRH and, consequently, in the premature reactivation of hypothalamic-pituitary-gonadal axis. The activation of excitatory factors or suppression of inhibitory factors during childhood represent the 2 major mechanisms of CPP, revealing a delicate balance of these opposing neuronal pathways. Hypothalamic hamartoma (HH) is the most well-known congenital cause of CPP with central nervous system abnormalities. Several mechanisms by which hamartoma causes CPP have been proposed, including an anatomical connection to the anterior hypothalamus, autonomous neuroendocrine activity in GnRH neurons, trophic factors secreted by HH, and mechanical pressure applied to the hypothalamus. The importance of genetic and/or epigenetic factors in the underlying mechanisms of CPP has grown significantly in the last decade, as demonstrated by the evidence of genetic abnormalities in hypothalamic structural lesions (eg, hamartomas, gliomas), syndromic disorders associated with CPP (Temple, Prader-Willi, Silver-Russell, and Rett syndromes), and isolated CPP from monogenic defects (MKRN3 and DLK1 loss-of-function mutations). Genetic and epigenetic discoveries involving the etiology of CPP have had influence on the diagnosis and familial counseling providing bases for potential prevention of premature sexual development and new treatment targets in the future. Global preventive actions inducing healthy lifestyle habits and less exposure to endocrine-disrupting chemicals during the lifespan are desirable because they are potentially associated with CPP.
- Pioneering studies on monogenic central precocious puberty(2019) CANTON, Ana Pinheiro Machado; SERAPHIM, Carlos Eduardo; BRITO, Vinicius Nahime; LATRONICO, Ana ClaudiaPubertal timing in humans is determined by complex interactions including hormonal, metabolic, environmental, ethnic, and genetic factors. Central precocious puberty (CPP) is defined as the premature reactivation of the hypothalamic-pituitary-gonadal axis, starting before the ages of 8 and 9 years in girls and boys, respectively; familial CPP is defined by the occurrence of CPP in two or more family members. Pioneering studies have evidenced the participation of genetic factors in pubertal timing, mainly identifying genetic causes of CPP in sporadic and familial cases. In this context, rare activating mutations were identified in genes of the kisspeptin excitatory pathway (KISS1R and KISS1 mutations). More recently, loss-of-function mutations in two imprinted genes (MKRN3 and DLK1) have been identified as important causes of familial CPP, describing novel players in the modulation of the hypothalamic-pituitary-gonadal axis in physiological and pathological conditions. MKRN3 mutations are the most common cause of familial CPP, and patients with MKRN3 mutations present clinical features indistinguishable from idiopathic CPP. Meanwhile, adult patients with DLK1 mutations present high frequency of metabolic alterations (overweight/obesity, early onset type 2 diabetes and hyperlipidemia), indicating that DLK1 may be a novel link between reproduction and metabolism.
- A new pathway in the control of the initiation of puberty: the MKRN3 gene(2015) ABREU, Ana Paula; MACEDO, Delanie B.; BRITO, Vinicius N.; KAISER, Ursula B.; LATRONICO, Ana ClaudiaPubertal timing is influenced by complex interactions among genetic, nutritional, environmental, and socioeconomic factors. The role of MKRN3, an imprinted gene located in the Prader-Willi syndrome critical region (chromosome 15q11-13), in pubertal initiation was first described in 2013 after the identification of deleterious MKRN3 mutations in five families with central precocious puberty (CPP) using whole-exome sequencing analysis. Since then, additional loss-of-function mutations of MKRN3 have been associated with the inherited premature sexual development phenotype in girls and boys from different ethnic groups. In all of these families, segregation analysis clearly demonstrated autosomal dominant inheritance with complete penetrance, but with exclusive paternal transmission, consistent with the monoallelic expression of MKRN3 (a maternally imprinted gene). Interestingly, the hypothalamic Mkrn3 mRNA expression pattern in mice correlated with a putative inhibitory input on puberty initiation. Indeed, the initiation of puberty depends on a decrease in factors that inhibit the release of GnRH combined with an increase in stimulatory factors. These recent human and animal findings suggest that MKRN3 plays an inhibitory role in the reproductive axis to represent a new pathway in pubertal regulation.
- Quality of life of patients with 46,XX and 46,XY disorders of sex development(2015) AMARAL, Rita Cassia; INACIO, Marlene; BRITO, Vinicius N.; BACHEGA, Tania A. S. S.; DOMENICE, Sorahia; ARNHOLD, Ivo J. P.; MADUREIRA, Guiomar; GOMES, Larissa; COSTA, Elaine M. F.; MENDONCA, Berenice B.Disorders of sex development (DSD) result from abnormalities in the complex process of sex determination and differentiation. An important consideration to guide the assignment of social sex in newborns with ambiguous genitalia is the quality of life (QoL) of these patients in adulthood. The rarity of most DSD conditions makes it difficult to conduct a long-term follow-up of affected patients through adulthood. This review of papers on the QoL of DSD patients evaluated in developing and developed countries by qualitative and quantitative instruments revealed a large spectrum of QoL, ranging from very poor to similar to, or even better than, the normal population. A more adequate QoL was found in patients from tertiary centres, indicating that the medical care of DSD patients should be multidisciplinary and carried out by specialized teams.
- Advances in the etiology, diagnosis and treatment of central precocious puberty(2014) MACEDO, Delanie B.; CUKIER, Priscilla; MENDONCA, Berenice B.; LATRONICO, Ana Claudia; BRITO, Vinicius NahimeThe onset of puberty is first detected as an increase in the amplitude and frequency of pulses of gonadotropin-releasing hormone (GnRH) after a quiescent period during childhood. The reemergence of pulsatile GnRH secretion leads to increases in the secretion of the gonadotropins, luteinizing hormone (LH), and follicle-stimulating hormone (FSH) by the pituitary gland, and the consequent activation of gonadal function. Early activation of the hypothalamic-pituitary-gonadal axis results in gonadotropin-dependent precocious puberty, also known as central precocious puberty (CPP), which is clinically defined by the development of secondary sexual characteristics before the age of 8 years in girls and 9 years in boys. Pubertal timing is influenced by complex interactions among genetic, nutritional, environmental, and socioeconomic factors. CPP is diagnosed on the basis of clinical signs of progressive pubertal development before the age of 8 years in girls and 9 years in boys, pubertal basal and/or GnRH-stimulated LH levels, and advanced bone age. Magnetic resonance imaging of the central nervous system is essential for establishing the CPP form as organic or idiopathic. Depot GnRH-analogues represent the first-line of therapy in CPP. Very recently, the genetic component of CPP was demonstrated by the evidence that the deficiency of the MKRN3 gene, located on long arm of chromosome 15, causes familial CPP in humans. In this current review, clinical and therapeutic aspects of the CPP will be discussed, contributing to adequate diagnosis and criterious approach of this relevant condition of pediatric endocrinology.