Endocrine Abstracts

Background: Cytochrome P450 side-chain cleavage enzyme (CYP11A1) catalyses the first and rate-limiting step of steroidogenesis. CYP11A1 firstly converts cholesterol into 22R-hydroxycholesterol, which relies on mitochondrial steroidogenic acute regulatory protein (StAR)-mediated cholesterol import. Two further StAR-independent CYP11A1 reactions facilitate pregnenolone biosynthesis. CYP11A1 deficiency is rare and manifests with adrenal insufficiency (AI), and, in 46,XY individua...

Background: 5α-Reductase type 2 deficiency (5ARD) is caused by mutations in the SRD5A2 gene. Inadequate masculinisation in XY individuals results from failure to convert testosterone (T) to dihydrotestosterone (DHT), a potent androgen. A decreased serum T:DHT ratio is frequently taken to identify 5ARD, but requires hCG stimulation for prepubertal patients; findings are not always supported by genotyping. Urine steroid profiling (USP) by GC-MS is established as showing sig...

The plasma membrane thyroid hormone (TH) transporter, MCT8, is present in the human placenta from early gestation and is postulated to participate in transplacental transfer of TH. In vitro, MCT8 overexpression decreases the survival of human cytotrophoblast in a TH-independent manner.Objective: To examine the role of Mct8 in fetoplacental growth using the Mct8 knockout (ko) mouse model.Methods: Heterozygous females were mat...

Thyroid hormones (THs) are important for fetal and placental development. Monocarboxylate transporters 8 and 10 (MCT8 and MCT10) are effective plasma membrane TH transporters expressed in the human placenta from 6 weeks of gestation. Both have been localized to human villous trophoblasts and extravillous trophoblasts (EVTs).Aims: Using HTR-8/SVneo cells as a model of 1st trimester EVTs, we assessed 1) T3 effects on gene expression, cell prolif...

Maternal thyroid hormones (THs) are important for fetoplacental development. We have previously reported lower fetal circulating concentration of THs in severe intrauterine growth restriction (IUGR) compared to gestationally-matched normal fetuses. The villous placental expression of TH receptors (TRs) and the TH transporter MCT8 is increased, whilst MCT10 expression is decreased, with severe IUGR.Objective: To assess the TH responsiveness of human cytot...

Thyroid hormones (TH) are important for the development of the fetus and placenta. Monocarboxylate transporter 8 (MCT8) is a potent plasma membrane TH transporter, present in the human placenta from 6 weeks of gestation. Its expression increases significantly with advancing gestational age. We postulate that MCT8 plays an important role in human placental development.Objective: To assess the effects of altered MCT8 expression on the survival, syncytialis...

Background: The identification of MRAP in 2005 as the first melanocortin-2-receptor (MC2R)/ACTH receptor accessory protein provided insight into the regulation of the melanocortin receptor system. Mutations in MRAP cause Familial glucocorticoid deficiency, an autosomal recessive disorder resulting in isolated cortisol deficiency. In vitro studies showed that MRAP was essential for the functional expression of the MC2R. The melanocortin receptor (MCR) family (MC1R to MC5...

Thyroid hormones (TH) are important for the development of the fetus and placenta. We have previously reported increased placental expression of the potent TH transporter, MCT8, with advancing gestation. The amino acid plasma membrane transporters, MCT10, LAT1, LAT2, and the organic anion transporters, OATP1A2 and OATP4A1, are also known to transport TH.Objective: To describe the ontogeny of these TH transporters and the obligate heterodimer of the LATs,...

Thyroid hormones play vital roles in fetal brain development. Mutations in MCT8, recently recognised as a specific thyroid hormone transporter, define a novel syndrome of severe X-linked psychomotor retardation and thyroid hormone resistance.N-TERA-2 (NT2) cells (human embryonal cells with characteristics of CNS precursors) were transiently transfected with either WT MCT8 or its L471P, R271H or S448X mutations, described in males affected by severe psych...

Thyroid hormones play a major role in the metabolic function of mammalian cells and are of particular importance in the development of the fetal brain. The MCT8 gene has recently been shown to encode an active and specific thyroid hormone transporter. Recent reports have identified mutations in the MCT8 gene in several unrelated boys presenting with severe X-linked psychomotor retardation and elevated serum T3.Ontogeny of mRNA encoding MCT8 was examined ...