[Enzymes involved in thyroid iodide organification]

Relationship of familial cytochrome P450 4V2 gene mutation with liver cirrhosis: A case report and review of the literature

BACKGROUND

Many genetic and metabolic diseases affect the liver, but diagnosis can be difficult because these diseases may have complex clinical manifestations and diverse clinical patterns. There is also incomplete clinical knowledge of these many different diseases and limitations of current testing methods.

CASE SUMMARY

We report a 53-year-old female from a rural area in China who was hospitalized for lower limb edema, abdominal distension, cirrhosis, and hypothyroidism. We excluded the common causes of liver disease (drinking alcohol, using traditional Chinese medicines, hepatitis virus infection, autoimmunity, and hepatolenticular degeneration). When she was 23-years-old, she developed night-blindness that worsened to complete blindness, with no obvious cause. Her parents were first cousins, and both were alive. Analysis of the patient’s family history indicated that all 5 siblings had night blindness and impaired vision; one sister was completely blind; and another sister had night-blindness complicated with cirrhosis and subclinical hypothyroidism. Entire exome sequencing showed that the patient, parents, and siblings all had mutations in the cytochrome P450 4V2 gene (CYP4V2). The CYP4V2 mutations of the parents and two sisters were heterozygous, and the others were homozygous. Two siblings also had heterozygous dual oxidase activator 2 (DUOXA2) mutations.

CONCLUSION

Mutations in the CYP4V2 gene may affect lipid metabolism and lead to chronic liver injury, fibrosis, and cirrhosis.

Environmentally relevant dose of the endocrine disruptor tributyltin disturbs redox balance in female thyroid gland

Tributyltin (TBT) is an endocrine disruptor used as a biocide in nautical paints. Even though many TBT effects in marine species are known, data in mammals are scarce, especially regarding the thyroid gland. The present study aimed to evaluate the effect of a subchronic exposure to TBT on thyroid oxidative stress of female Wistar rats. Rats received vehicle (control group), 200 or 1000 ng TBT/kg body weight/day for 40 days. After euthanasia, one part of the thyroids were collected in order to assess iodide uptake; activity and/or mRNA expression of thyroperoxidase (TPO) and dual oxidases (DUOXs); activity and/or mRNA expression of catalase, glutathione peroxidase, superoxide dismutase and NADPH oxidase 4 (CAT, GPx, SOD and NOX4); 4-hydroxynonenal (4-HNE) expression and total thiol groups levels; and mRNA expression of estrogen receptors alpha and beta (ERα and ERβ). The remaining part of the thyroid was processed for morphological analysis of estrogen receptor alpha (ERα) and for collagen deposition. Iodide uptake was not changed with treatments. TPO activity and expression were increased in the TBT1000 group (259.81% and 95.17%). The activity, but not mRNA, of CAT (17.36% TBT200; 27.10% TBT1000) and GPx (29.24% TBT200; 28.97% TBT1000) were decreased by TBT. SOD and NADPH oxidase activity, as well as thiol group and 4-HNE levels remained unchanged. Interstitial collagen deposition increased in the TBT200 group (39.54%). The mRNA expression of ERα increased in TBT-treated rats (44.87% TBT200; 36.43% TBT1000), while protein expression was increased but not reaching significance (TBT1000, p = 0.056) by TBT. Therefore, our results show that TBT increases TPO expression and reduces antioxidant enzyme activities in the thyroid gland leading to oxidative stress. Some of these effects could be mediated by the ERα pathway.

Gene mutations in children with permanent congenital hypothyroidism in Yunnan, China

OBJECTIVE

To investigate molecular and clinical characteristics of children with permanent congenital hypothyroidism (CH) in Yunnan, China.

METHODS

The clinical data of 40 children with CH diagnosed and treated in the First People's Hospital of Yunnan Province during January 2016 and January 2019 were retrospectively analyzed. All children were followed up to 3 years old, and Gesell intelligent score was evaluated at age of 1, 2 and 3 years, respectively. Developmental status and prognosis were evaluated. Next-generation sequencing (NGS) was used to screen all exons and exon-intron boundary sequences of the 27 known CH associated genes, and the relationship between genotypes and clinical phenotypes was analyzed.

RESULTS

Among the 40 children, the thyroid related pathogenic gene mutations were detected in 23 cases with a rate of 57.5%, and a total of 32 mutations of 8 genes were detected. Mutations in DUOX2, TPO and TSHR genes were the most common ones with mutation frequencies of 65.9%(29/44), 11.4%(5/44) and 9.1%(4/44), respectively. DUOX2 gene mutations were detected in 17 children with CH, and a total of 17 mutation types were detected. p.K530* was the most common mutation in DUOX2 gene, accounting for 20.7%(6/29). There was no significant difference in physical development and intelligence assessment between children with DUOX2 heterozygous mutation and compound heterozygous mutations. None of patients could terminate medication at 3 years of the follow-up and all of them were provisionally assessed as permanent CH. The physical and mental development assessment of children with other gene mutations were also in the normal range.

CONCLUSION

The detection rate of DUOX2, TPO and TSHR pathogenic mutations are high among children with permanent CH in Yunnan area, and no correlation is observed between gene mutation types and prognosis in children with CH.

The Role of Zinc in Thyroid Hormones Metabolism

Abstract. Thyroid hormones play an important role in body homeostasis by facilitating metabolism of lipids and glucose, regulating metabolic adaptations, responding to changes in energy intake, and controlling thermogenesis. Proper metabolism and action of these hormones requires the participation of various nutrients. Among them is zinc, whose interaction with thyroid hormones is complex. It is known to regulate both the synthesis and mechanism of action of these hormones. In the present review, we aim to shed light on the regulatory effects of zinc on thyroid hormones. Scientific evidence shows that zinc plays a key role in the metabolism of thyroid hormones, specifically by regulating deiodinases enzymes activity, thyrotropin releasing hormone (TRH) and thyroid stimulating hormone (TSH) synthesis, as well as by modulating the structures of essential transcription factors involved in the synthesis of thyroid hormones. Serum concentrations of zinc also appear to influence the levels of serum T3, T4 and TSH. In addition, studies have shown that Zinc transporters (ZnTs) are present in the hypothalamus, pituitary and thyroid, but their functions remain unknown. Therefore, it is important to further investigate the roles of zinc in regulation of thyroid hormones metabolism, and their importance in the treatment of several diseases associated with thyroid gland dysfunction.

Use of potassium iodide in dermatology: updates on an old drug

Potassium iodide, as a saturated solution, is a valuable drug in the dermatologist's therapeutic arsenal and is useful for the treatment of different diseases due to its immunomodulatory features. However, its prescription has become increasingly less frequent in dermatology practice. Little knowledge about its exact mechanism of action, lack of interest from the pharmaceutical industry, the advent of new drugs, and the toxicity caused by the use of high doses of the drug are some possible explanations for that. Consequently, there are few scientific studies on the pharmacological aspects, dosage and efficacy of this drug. Also, there is no conventional standard on how to manipulate and prescribe the saturated solution of potassium iodide, which leads to unawareness of the exact amount of the salt being delivered in grams to patients. Considering that dosage is directly related to toxicity and the immunomodulatory features of this drug, it is essential to define the amount to be prescribed and to reduce it to a minimum effective dose in order to minimize the risks of intolerance and thus improve treatment adherence. This review is relevant due to the fact that the saturated solution of potassium iodide is often the only therapeutic choice available for the treatment of some infectious, inflammatory and immune-mediated dermatoses, no matter whether the reason is specific indication, failure of a previous therapy or cost-effectiveness.

A novel dual oxidase maturation factor 2 gene mutation for congenital hypothyroidism

Congenital hypothyroidism (CH) is caused by thyroid hormone deficiency present at birth. DUOXA2 (dual oxidase maturation factor 2) is one of the prerequisites for thyroid hormone synthesis. The present study explored the novel mutations of DUOXA2 in CH patients. Genomic DNA was extracted from peripheral blood of 47 unrelated CH patients, their family members and 100 healthy controls. All 6 exons and their flanking sequences of the DUOXA2 gene were PCR amplified and sequenced. Sequencing results were compared with the standard. Compound heterozygosity with DUOXA2 gene mutations at c.413-414insA (Y138X) and c.738C>G (Y246X) was identified in one patient, and absent in 100 healthy controls. Among them, the c.413‑414insA (Y138X) mutation was a novel one. The patient with the c.413-414insA (Y138X) mutation had mild CH symptoms. This study is the first to report a novel c.413-414insA (Y138X) mutation for CH, thereby expanding the mutational spectrum of the DUOXA2 gene.

Abuso de esteróides anabolizantes e seu impacto sobre a função tireóidea

A utilização de esteróides anabolizantes por indivíduos que desejam aumentar sua performance física, ou simplesmente para fins estéticos, tem atingido índices alarmantes nas últimas três décadas. Além dos efeitos desejados, uma infinidade de efeitos colaterais já foi bem descrita na literatura, como vários tipos de câncer, ginecomastia, peliosis hepatis, insuficiência renal, virilização, dentre outros. Sobre a função tireóidea, o efeito mais pronunciado em seres humanos é a diminuição da TBG, com conseqüente diminuição sérica de T3 e T4 totais, dependendo, porém, da susceptibilidade da molécula à aromatização e conseqüente transformação em estrógeno. Em ratos, o tratamento com esteróides anabolizantes altera a metabolização periférica dos hormônios tireóideos e também parece causar importante efeito proliferativo sobre as células tireóideas. Assim, o presente artigo visa rever os dados publicados acerca dos efeitos de doses suprafisiológicas de esteróides anabolizantes sobre a função tireóidea, reforçando o perigo que a utilização indiscriminada dessas drogas pode causar à saúde.