A Case-Control Study of the Relationship Between Genetic Polymorphism and Cretinism in Xinjiang

Background

Cretinism is a subtype of congenital hypothyroidism, an endocrine disorder resulting from inadequate thyroid hormone production or receptor deficiency. Genetic abnormalities play a major role in the development of thyroid dysfunction.

Methods

We recruited 183 participants with cretinism and 119 healthy participants from the Xinjiang Uyghur Autonomous Region and randomly selected 29 tag single nucleotide polymorphisms (tSNPs) in TSHB, PAX8, TPO, NKX2-5, and TSHR in all participants. We compared genotype and allele frequencies between cases and controls utilizing the chi-squared test, logistic regression analysis, and haplotype analysis.

Results

Using the chi-squared test, a single SNP was found to be associated with cretinism (recessive model: rs3754363, OR = 0.46, 95% CI = 0.27-0.80, P = 0.00519; genotype model: P = 0.01677). We stratified neurological, myxedematous, and mixed type and determined that another SNP was associated with a higher risk when comparing myxedematous type to the neurological type (rs2277923).

Conclusion

rs3754363 has a statistically significant protective effect on people with cretinism, while rs2277923 may play a greater role in promoting the development of neurocretinism.

The Prevention of Iodine Deficiency: A History

Iodine is an essential component of the hormones produced by the thyroid gland and is, therefore, essential for mammalian life. A landmark trial in the early 20th century definitively demonstrated that iodine supplementation could prevent what was then known as "endemic goiter." Subsequent studies over the next decades demonstrated that iodine deficiency causes a spectrum of disease, including not just goiter, but also cretinism, intellectual impairment, and adverse obstetric outcomes. Salt iodization, first used in Switzerland and the United States in the1920s, has become the mainstay of iodine deficiency prevention efforts. The dramatic reduction in the global prevalence of iodine deficiency disorders (IDD) over the past 30 years represents an outstanding and under-recognized public health achievement. This narrative review provides an overview of critical scientific discoveries and advances in public health nutrition related to the prevention of IDD in the United States and worldwide. This review was written to commemorate the centennial of the founding of the American Thyroid Association.

Gene therapy targeting the blood-brain barrier improves neurological symptoms in a model of genetic MCT8 deficiency

A genetic deficiency of the solute carrier monocarboxylate transporter 8 (MCT8), termed Allan-Herndon-Dudley syndrome, is an important cause of X-linked intellectual and motor disability. MCT8 transports thyroid hormones across cell membranes. While thyroid hormone analogues improve peripheral changes of MCT8 deficiency, no treatment of the neurological symptoms is available so far. Therefore, we tested a gene replacement therapy in Mct8- and Oatp1c1-deficient mice as a well-established model of the disease. Here, we report that targeting brain endothelial cells for Mct8 expression by intravenously injecting the vector AAV-BR1-Mct8 increased tri-iodothyronine (T3) levels in the brain and ameliorated morphological and functional parameters associated with the disease. Importantly, the therapy resulted in a long-lasting improvement in motor coordination. Thus, the data support the concept that MCT8 mediates the transport of thyroid hormones into the brain and indicate that a readily accessible vascular target can help overcome the consequences of the severe disability associated with MCT8 deficiency.

Comparison of Salt Iodization Requirements in National Standards with Global Guidelines

Background

Food fortification is the addition of 1 or more micronutrients to commonly consumed foods and is utilized by many countries as a public health intervention to prevent and control micronutrient deficiencies. As iodine deficiency was a major public health issue globally, the WHO developed evidence-based guidelines for the fortification of salt with iodine. The implementation of salt iodization has been highly successful in reducing iodine deficiency disorders worldwide and is recommended as the main strategy to prevent iodine deficiency.

Objectives

This analysis compared salt iodization requirements specified in countries' salt standards with WHO 2014 Guidelines on salt fortification.

Methods

For countries with mandatory salt iodization legislation, data from the Global Fortification Data Exchange regarding iodine amounts and iodine compounds, to be added to salt per the country standard and corresponding national salt intake quantities, were compared with 2014 WHO Guidelines.

Results

As of 4 September 2021, 110 countries with mandatory salt iodization legislation had national salt standards that specified iodine amounts and compounds and salt intake data. All but 1 specified at least 1 recommended iodine compound, but the majority specified higher iodine amounts in salt standards than indicated in the guidelines, taking salt consumption levels into account. Our analysis did not find excess iodine intake as a result; however, we did not have data on the extent of compliance with national salt standards.

Conclusions

Existing iodization requirements in salt standards appear to be appropriate for most countries. Countries in which iodine amounts in salt standards are significantly higher than those recommended in the 2014 Guidelines, in particular those with low compliance with national standards or excess iodine intake, may wish to review program process and output indicators and assess whether current iodine amounts in standards would result in excessive intake if implementation was improved.

Pseudo-pheochromocytoma due to obstructive sleep apnea: a case report

SUMMARY

Obstructive sleep apnea (OSA) is a condition of intermittent nocturnal upper airway obstruction. OSA increases sympathetic drive which may result in clinical and biochemical features suggestive of pheochromocytoma. We present the case of a 65-year-old male with a 2.9-cm left adrenal incidentaloma on CT, hypertension, symptoms of headache, anxiety and diaphoresis, and persistently elevated 24-h urine norepinephrine (initially 818 nmol/day (89-470)) and normetanephrine (initially 11.2 µmol/day (0.6-2.7)). He was started on prazosin and underwent left adrenalectomy. Pathology revealed an adrenal corticoadenoma with no evidence of pheochromocytoma. Over the next 2 years, urine norepinephrine and normetanephrine remained significantly elevated with no MIBG avid disease. Years later, he was diagnosed with severe OSA and treated with continuous positive airway pressure. Urine testing done once OSA was well controlled revealed complete normalization of urine norepinephrine and normetanephrine with substantial symptom improvement. It was concluded that the patient never had a pheochromocytoma but rather an adrenal adenoma with biochemistry and symptoms suggestive of pheochromocytoma due to untreated severe OSA. Pseudo-pheochromocytoma is a rare presentation of OSA and should be considered on the differential of elevated urine catecholamines and metanephrines in the right clinical setting.

LEARNING POINTS

Obstructive sleep apnea (OSA) is a common condition among adults. OSA may rarely present as pseudo-pheochromocytoma with symptoms of pallor, palpitations, perspiration, headache, or anxiety. OSA should be considered on the differential of elevated urine catecholamines and metanephrines, especially in patients with negative metaiodobenzylguanidine (MIBG) scan results.

Emergency Surgery in a Child with Cretinism with Anticipated Difficult Airway Under Low-Dose Subarachnoid Block

A child with cretinism poses multiple anaesthetic challenges due to the associated mental and physical disability, deranged metabolic and physiologic functions, difficult airway and propensity to perioperative cardiorespiratory complications. Spinal anaesthesia in children is associated with remarkable cardiorespiratory stability and provides complete surgical anaesthesia. Here, we report a case that describes the first successful anaesthetic management of a child who was an unevaluated case of cretinism under subarachnoid block.

Iodine consumption and cognitive performance: Confirmation of adequate consumption

Iodine, a dynamic nutrient present in thyroid hormones, is responsible for regulating thyroid function, supporting a healthy metabolism, and aiding growth and development. Iodine is also essential for brain development during specific time windows influencing neurogenesis, neuronal and glial cell differentiation, myelination, neuronal migration, and synaptogenesis. About 1.5 billion people in 130 countries live in areas at risk of iron deficiencies (IDs). Reduced mental ability due to IDs occurs in almost 300 million people. Ensuring the consumption of minimum recommended daily allowances of iodine remains challenging. The effects of ID disorders range from high mortality of fetuses and children to inhibited mental development (cretinism). Poor socioeconomic development and impaired school performance are also notable. Currently, ID disorders are the single greatest contributor to preventable brain damage in fetuses and infants and arrested psychomotor development in children. Iodized salt may help fulfill iodine requirements. Increases in food salt iodization programs can help overcome ID disorders. Dietary plans can be well adjusted to incorporate iodinated foods. Maternal iodine supplementation for offspring requires adequate attention. Fruits, vegetables, bread, eggs, legumes (beans and peas), nuts, seeds, seafood, lean meats and poultry, and soy products provide small quantities of iodine. Nutrient-dense foods containing essential vitamins and minerals such as iodine may confer positive effects. To some extent, fortified foods and daily dietary supplements can be provided for different nutrients including iodine; otherwise, iodine may be consumed in less than the recommended amounts. This review focuses on aspects of adequate iodine consumption to avoid cognitive impairments.

Endocrinology and the arts at the feet of the dancing Lord: Parathyroid hormone resistance in an Indian icon

The dance of Siva has a cosmic appeal. Nowhere has this dance been crystallised in its pristine form as in the Nataraja Bronzes from the Chola period. Mysticism surrounds the dancing form of the Nataraja. But does Nataraja dance upon an endocrine mystery. Does the demon under his feet Apasmara literally forgetfulness or epilepsy have an endocrine disorder. The short limbed stocky eye popping dwarf with possible mental retardation with a name that suggests epilepsy throws open a host of endocrine diagnoses. From cretinisim to the original descriptions of pseudohypoparathyroidism here is one view of the medical mystery under Shiva's dancing feet.

Role of maternal thyroid hormones in the developing neocortex and during human evolution

The importance of thyroid hormones during brain development has been appreciated for many decades. In humans, low levels of circulating maternal thyroid hormones, e.g., caused by maternal hypothyroidism or lack of iodine in diet, results in a wide spectrum of severe neurological defects, including neurological cretinism characterized by profound neurologic impairment and mental retardation, underlining the importance of the maternal thyroid hormone contribution. In fact, iodine intake, which is essential for thyroid hormone production in the thyroid gland, has been related to the expansion of the brain, associated with the increased cognitive capacities during human evolution. Because thyroid hormones regulate transcriptional activity of target genes via their nuclear thyroid hormone receptors (THRs), even mild and transient changes in maternal thyroid hormone levels can directly affect and alter the gene expression profile, and thus disturb fetal brain development. Here we summarize how thyroid hormones may have influenced human brain evolution through the adaptation to new habitats, concomitant with changes in diet and, therefore, iodine intake. Further, we review the current picture we gained from experimental studies in rodents on the function of maternal thyroid hormones during developmental neurogenesis. We aim to evaluate the effects of maternal thyroid hormone deficiency as well as lack of THRs and transporters on brain development and function, shedding light on the cellular behavior conducted by thyroid hormones.

Iodine deficiency in pregnancy: the effect on neurodevelopment in the child

Iodine is an integral part of the thyroid hormones, thyroxine (T₄) and tri-iodothyronine (T₃), necessary for normal growth and development. An adequate supply of cerebral T₃, generated in the fetal brain from maternal free T₄ (fT₄), is needed by the fetus for thyroid hormone dependent neurodevelopment, which begins in the second half of the first trimester of pregnancy. Around the beginning of the second trimester the fetal thyroid also begins to produce hormones but the reserves of the fetal gland are low, thus maternal thyroid hormones contribute to total fetal thyroid hormone concentrations until birth. In order for pregnant women to produce enough thyroid hormones to meet both her own and her baby’s requirements, a 50% increase in iodine intake is recommended. A lack of iodine in the diet may result in the mother becoming iodine deficient, and subsequently the fetus. In iodine deficiency, hypothyroxinemia (i.e., low maternal fT₄) results in damage to the developing brain, which is further aggravated by hypothyroidism in the fetus. The most serious consequence of iodine deficiency is cretinism, characterised by profound mental retardation. There is unequivocal evidence that severe iodine deficiency in pregnancy impairs brain development in the child. However, only two intervention trials have assessed neurodevelopment in children of moderately iodine deficient mothers finding improved neurodevelopment in children of mothers supplemented earlier rather than later in pregnancy; both studies were not randomised and were uncontrolled. Thus, there is a need for well-designed trials to determine the effect of iodine supplementation in moderate to mildly iodine deficient pregnant women on neurodevelopment in the child.

Are the small human-like fossils found on Flores human endemic cretins?

Fossils from Liang Bua (LB) on Flores, Indonesia, including a nearly complete skeleton (LB1) dated to 18kyr BP, were assigned to a new species, Homo floresiensis. We hypothesize that these individuals are myxoedematous endemic (ME) cretins, part of an inland population of (mostly unaffected) Homo sapiens. ME cretins are born without a functioning thyroid; their congenital hypothyroidism leads to severe dwarfism and reduced brain size, but less severe mental retardation and motor disability than neurological endemic cretins. We show that the fossils display many signs of congenital hypothyroidism, including enlarged pituitary fossa, and that distinctive primitive features of LB1 such as the double rooted lower premolar and the primitive wrist morphology are consistent with the hypothesis. We find that the null hypothesis (that LB1 is not a cretin) is rejected by the pituitary fossa size of LB1, and by multivariate analyses of cranial measures. We show that critical environmental factors were potentially present on Flores, how remains of cretins but not of unaffected individuals could be preserved in caves, and that extant oral traditions may provide a record of cretinism.

[REShENNYE I NEREShENNYE VOPROSY ENDEMIChESKOGO ZOBA I YODTsEFITsITNYKh SOSTOYaNIY (LEKTsIYa)]

Iodine deficiency, in addition to the development of an enlargement of the thyroid gland - goiter, leads to a number of other pathological conditions, which are commonly called iodine deficiency diseases. The spectrum of iodine deficiency diseases is wide and depends on the period of life when iodine deficiency affects the body. Iodine deficiency during pregnancy and embryonic development leads to a high prevalence of spontaneous abortion, especially in the first trimester of pregnancy; high perinatal and infant mortality, congenital malformations, congenital hypothyroidism with a lag in physical and mental development. In childhood and adolescence, iodine deficiency is accompanied by an increase in the thyroid gland, in some cases with a violation or delay in physical, mental and sexual development. In the mature period, iodine deficiency is accompanied by varying degrees of thyroid enlargement. Cretinism in iodine-deficient areas occurs with a frequency of 1 to 10%.

Brain glucose utilization in mice with a targeted mutation in the thyroid hormone alpha or beta receptor gene

Brain glucose utilization is markedly depressed in adult rats made cretinous after birth. To ascertain which subtype of thyroid hormone (TH) receptors, TRalpha1 or TRbeta, is involved in the regulation of glucose utilization during brain development, we used the 2-[(14)C]deoxyglucose method in mice with a mutation in either their TRalpha or TRbeta gene. A C insertion produced a frameshift mutation in their carboxyl terminus. These mutants lacked TH binding and transactivation activities and exhibited potent dominant negative activity. Glucose utilization in the homozygous TRbetaPV mutant mice and their wild-type siblings was almost identical in 19 brain regions, whereas it was markedly reduced in all brain regions of the heterozygous TRalpha1PV mice. These suggest that the alpha1 receptor mediates the TH effects in brain. Inasmuch as local cerebral glucose utilization is closely related to local synaptic activity, we also examined which thyroid hormone receptor is involved in the expression of synaptotagmin-related gene 1 (Srg1), a TH-positively regulated gene involved in the formation and function of synapses [Thompson, C. C. (1996) J. Neurosci. 16, 7832-7840]. Northern analysis showed that Srg1 expression was markedly reduced in the cerebellum of TRalpha(PV/+) mice but not TRbeta(PV/PV) mice. These results show that the same receptor, TRalpha1, is involved in the regulation by TH of both glucose utilization and Srg1 expression.