Effects of hyperthyroidism in the development of the appendicular skeleton and muscles of zebrafish, with notes on evolutionary developmental pathology (Evo-Devo-Path).

The hypothalamus-pituitary-thyroid (HPT) axis plays a crucial role in the metabolism, homeostasis, somatic growth and development of teleostean fishes. Thyroid hormones regulate essential biological functions such as growth and development, regulation of stress, energy expenditure, tissue compound, and psychological processes. Teleost thyroid follicles produce the same thyroid hormones as in other vertebrates: thyroxin (T4) and triiodothyronine (T3), making the zebrafish a very useful model to study hypo- and hyperthyroidism in other vertebrate taxa, including humans. Here we investigate morphological changes in T3 hyperthyroid cases in the zebrafish to better understand malformations provoked by alterations of T3 levels. In particular, we describe musculoskeletal abnormalities during the development of the zebrafish appendicular skeleton and muscles, compare our observations with those recently done by us on the normal developmental of the zebrafish, and discuss these comparisons within the context of evolutionary developmental pathology (Evo-Devo-Path), including human pathologies.

Iodine Deficiency and Supplementation in Pregnancy.

Iodine deficiency during pregnancy is an important global public health issue and the leading preventable cause of neurodevelopmental impairments worldwide. The effects of severe iodine deficiency during pregnancy, including adverse obstetric outcomes and decreased child intelligence quotient, have been clearly established. However, the effects of mild-to-moderate deficiency remain less well understood. Pregnant and lactating women have higher iodine requirements than other adults; intakes of 220 to 250 µg/d in pregnancy and 250 to 290 µg/d in lactation. In this article, we describe iodine metabolism, iodine requirements in pregnancy and lactation, the effects of both iodine deficiency and excessive iodine intakes in pregnancy, and the efficacy of iodine supplementation.

The effect of iodine deficiency during pregnancy on child development.

It is well known that severe iodine deficiency during pregnancy may cause impaired brain development in the child, with effects on cognitive and motor function, hearing and speech. Whether mild-to-moderate deficiency also affects neurological development is less well known, but in the past decade a number of observational studies have been conducted to answer this question and these studies are reviewed in this article. The picture is now emerging that even mild-to-moderate iodine deficiency during pregnancy may be associated with subtle impairments in cognition and school performance, although the evidence from randomised controlled trials is still lacking. As global efforts to eradicate iodine deficiency in populations continue, it is more likely that mild-to-moderate, rather than severe, iodine deficiency will be the issue of concern in pregnancy, and therefore further research in regions of mild-to-moderate deficiency is required to strengthen the research base and to inform public-health policy.

Toxicity and non-harmful effects of the soya isoflavones, genistein and daidzein, in embryos of the zebrafish, Danio rerio.

Based on the assumed oestrogenic and apoptotic properties of soya isoflavones (genistein, daidzein), and following the current OECD test-guidelines and principle of 3Rs, we have studied the potential toxicity of phytochemicals on the zebrafish embryos test (ZFET). For this purpose, zebrafish embryos at 2-3 h post-fertilisation (hpf) were exposed to both soya isoflavones (from 1.25 mg/L to 20 mg/L) and assayed until 96 hpf. Lethal and sub-lethal endpoints (mortality, hatching rates and malformations) were estimated in the ZFET, which was expanded to potential gene expression markers, determining the lowest observed effect (and transcriptional) concentrations (LOEC, LOTEC), and the no-observable effect (and transcriptional) concentrations (NOEC, NOTEC). The results revealed that genistein is more toxic (LC50-96 hpf: 4.41 mg/L) than daidzein (over 65.15 mg/L). Both isoflavones up-regulated the oestrogen (esrrb) and death receptors (fas) and cyp1a transcript levels. Most thyroid transcript signals were up-regulated by genistein (except for thyroid peroxidase/tpo), and the hatching enzyme (he1a1) was exclusively up-regulated by daidzein (from 1.25 mg/L onwards). The ZFET proved suitable for assessing toxicant effects of both isoflavones and potential disruptions (i.e. oestrogenic, apoptotic, thyroid, enzymatic) during the embryogenesis and the endotrophic larval period.

The Effects of Disturbance on Hypothalamus-Pituitary-Thyroid (HPT) Axis in Zebrafish Larvae after Exposure to DEHP.

Di-(2-ethylhexyl) phthalate (DEHP) has the potential to disrupt the thyroid endocrine system, but the underlying mechanism is unknown. In this study, zebrafish (Danio rerio) embryos were exposed to different concentrations of DEHP (0, 40, 100, 200, 400 µg/L) from 2 to 168 hours post fertilization (hpf). Thyroid hormones (THs) levels and transcriptional profiling of key genes related to hypothalamus-pituitary-thyroid (HPT) axis were examined. The result of whole-body thyroxine (T4) and triiodothyronine (T3) indicated that the thyroid hormone homeostasis was disrupted by DEHP in the zebrafish larvae. After exposure to DEHP, the mRNA expressions of thyroid stimulating hormone (tshß) and corticotrophin releasing hormone (crh) genes were increased in a concentration dependent manner, respectively. The expression level of genes involved in thyroid development (nkx2.1 and pax8) and thyroid synthesis (sodium/iodide symporter, nis, thyroglobulin, tg) were also measured. The transcripts of nkx2.1 and tg were significantly increased after DEHP exposure, while those of nis and pax8 had no significant change. Down-regulation of uridinediphosphate-glucuronosyl-transferase (ugt1ab) and up-regulation of thyronine deiodinase (dio2) might change the THs levels. In addition, the transcript of transthyretin (ttr) was up-regulated, while the mRNA levels of thyroid hormone receptors (trα and trß) remained unchanged. All the results demonstrated that exposure to DEHP altered the whole-body thyroid hormones in the zebrafish larvae and changed the expression profiling of key genes related to HPT axis, proving that DEHP induced the thyroid endocrine toxicity and potentially affected the synthesis, regulation and action of thyroid hormones.

Maternal Iodine Exposure: A Case of Fetal Goiter and Neonatal Hearing Loss.

A 27-year-old gravid 1 at 27 weeks 6 days with a history of hypothyroidism had an ultrasound that demonstrated a 3.9 × 3.2 × 3.3-cm well-circumscribed anterior neck mass, an extended fetal head, and polyhydramnios. Further characterization by magnetic resonance imaging (MRI) showed a fetal goiter. During her evaluation for the underlying cause of the fetal goiter, the patient revealed she was taking nutritional iodine supplements for treatment of her hypothyroidism. She was ingesting 62.5 times the recommended amount of daily iodine in pregnancy. The excessive iodine consumption caused suppression of the fetal thyroid hormone production, resulting in hypothyroidism and goiter formation. After the iodine supplement was discontinued, the fetal goiter decreased in size. At delivery, the airway was not compromised. The infant was found to have reversible hypothyroidism and bilateral hearing loss postnatally. This case illustrates the importance of examining for iatrogenic causes for fetal anomalies, especially in unregulated nutritional supplements.

Therapy of endocrine disease: Impact of iodine supplementation in mild-to-moderate iodine deficiency: systematic review and meta-analysis.

BACKGROUND: Although the detrimental effects of severe iodine deficiency are well recognised, the benefits of correcting mild-to-moderate iodine deficiency are uncertain. OBJECTIVES: We undertook a systematic review of the impact of iodine supplementation in populations with mild-to-moderate iodine deficiency. METHODS: We searched Medline and the Cochrane library for relevant articles published between January 1966 and April 2013, which investigated the effect of iodine supplementation on maternal and newborn thyroid function, infant neurodevelopment and cognitive performance in school-age children. The quality of studies was graded and eligible trials were evaluated in the meta-analysis. RESULTS: Nine randomised controlled trials (RCTs) and eight observational studies met the inclusion criteria. Controlled trials on infant neurodevelopment were lacking; gestational iodine supplementation reduced maternal thyroid volume and serum thyroglobulin and in some studies prevented a rise in serum thyroid-stimulating hormone. None of the intervention trials recorded an excess frequency of thyroid dysfunction in contrast to observational studies. A pooled analysis of two RCTs which measured cognitive function in school-age children showed modest benefits of iodine supplementation on perceptual reasoning (standardised mean difference (SMD) 0.55; 95% CI 0.05, 1.04; P=0.03) and global cognitive index (SMD 0.27; 95% CI 0.10, 0.44; P=0.002) with significant heterogeneity between studies. CONCLUSION: Iodine supplementation improves some maternal thyroid indices and may benefit aspects of cognitive function in school-age children, even in marginally iodine-deficient areas. Further large prospective controlled studies are urgently required to clarify these findings and quantify the risk/benefits of iodine supplementation in regions previously believed to be iodine sufficient such as the UK.

[Iodine intake during pregnancy: effects on thyroid function in mother and child]. / Ingesta de yodo durante el embarazo: efectos en la función tiroidea materna y neonatal.

INTRODUCTION: Recent studies in Spain have shown an inadequate iodine intake in a significant proportion of pregnant women. Pregnancy increases thyroid hormone requirements, and adequate iodine intake is therefore needed. MATERIAL AND METHODS: One hundred and forty-seven women in their third trimester (week 37) of pregnancy provided a blood sample and a 24-hour urine sample to test serum and urine iodine levels and completed a food frequency questionnaire to assess iodine intake during pregnancy. Serum TSH levels were measured in the babies born to the 140 mothers in the postpartum group. RESULTS: Only 10.9% of pregnant women consumed more than 250 µg iodine daily, and 24.4% of them consumed less than 100 µg daily. Mean free T4 levels were 9.37 pmol/L, and 74 women (54.41%) had levels below the hypothyroxinemia threshold. TSH levels were normal in 135 newborns (96.4%), while 5 (3.6%) had levels higher than 5 µU/mL.

Maternal high-fat diet modulates the fetal thyroid axis and thyroid gene expression in a nonhuman primate model.

Thyroid hormone (TH) is an essential regulator of both fetal development and energy homeostasis. Although the association between subclinical hypothyroidism and obesity has been well studied, a causal relationship has yet to be established. Using our well-characterized nonhuman primate model of excess nutrition, we sought to investigate whether maternal high-fat diet (HFD)-induced changes in TH homeostasis may underlie later in life development of metabolic disorders and obesity. Here, we show that in utero exposure to a maternal HFD is associated with alterations of the fetal thyroid axis. At the beginning of the third trimester, fetal free T(4) levels are significantly decreased with HFD exposure compared with those of control diet-exposed offspring. Furthermore, transcription of the deiodinase, iodothyronine (DIO) genes, which help maintain thyroid homeostasis, are significantly (P < 0.05) disrupted in the fetal liver, thyroid, and hypothalamus. Genes involved in TH production are decreased (TRH, TSHR, TG, TPO, and SLC5A5) in hypothalamus and thyroid gland. In experiments designed to investigate the molecular underpinnings of these observations, we observe that the TH nuclear receptors and their downstream regulators are disrupted with maternal HFD exposure. In fetal liver, the expression of TH receptor ß (THRB) is increased 1.9-fold (P = 0.012). Thorough analysis of the THRB promoter reveals a maternal diet-induced alteration in the fetal THRB histone code, alongside differential promoter occupancy of corepressors and coactivators. We speculate that maternal HFD exposure in utero may set the stage for later in life obesity through epigenomic modifications to the histone code, which modulates the fetal thyroid axis.

Endocrine disorders in pregnancy: physiological and hormonal aspects of pregnancy.

The endocrinology of pregnancy involves endocrine and metabolic changes as a consequence of physiological alterations at the foetoplacental boundary between mother and foetus. The vast changes in maternal hormones and their binding proteins complicate assessment of the normal level of most hormones during gestation. The neuroendocrine events and their timing in the placental, foetal and maternal compartments are critical for initiation and maintenance of pregnancy, for foetal growth and development, and for parturition. As pregnancy advances, the relative number of trophoblasts increase and the foeto-maternal exchange begins to be dominated by secretory function of the placenta. As gestation progresses toward term, the number of cytotrophoblasts again declines and the remaining syncytial layer becomes thin and barely visible. This arrangement facilitates transport of compounds including hormones and their precursors across the foeto-maternal interface. The endocrine system is the earliest system developing in foetal life, and it is functional from early intrauterine existence through old age. Regulation of the foetal endocrine system relies, to some extent, on precursors secreted by placenta and/or mother.

Neonatal thyroid function: effect of a single exposure to iodinated contrast medium in utero.

PURPOSE: To evaluate the effect of in utero exposure to a single dose of water-soluble intravenous iodinated contrast medium on thyroid function at birth. MATERIALS AND METHODS: This study was approved by the institutional review board, with waiver of consent, and was HIPAA compliant. Maternal and newborn records were retrospectively reviewed. All pregnant women who underwent multidetector pulmonary computed tomographic angiography because they were suspected of having pulmonary embolism between 2004 and 2008 and newborns resulting from the index pregnancy were included. In all examinations, iohexol was used as the contrast agent. Dose and amount of contrast agent and gestational age at the time of administration of the contrast agent were collected, and thyroxine (T(4)) and thyroid-stimulating hormone (TSH) levels were measured at birth. A total of 344 maternal and 343 newborn records were reviewed. A descriptive analysis was performed, and means, standard deviations, and confidence intervals were reported. RESULTS: Mean gestational age at the time of administration of the contrast material was 27.8 weeks +/- 7.4. The mean dose of total iodine administered was 45,000 mg/L +/- 7321. All newborns had a normal T(4) level at birth; only one newborn had a transiently abnormal TSH level at birth, which normalized at day 6 of life. This newborn was born to a mother who had many drug exposures during pregnancy. CONCLUSION: A single, high-dose in utero exposure to water-soluble, low-osmolar, iodinated intravenous products, such as iohexol, is unlikely to have a clinically important effect on thyroid function at birth.

Clinical and biological consequences of iodine deficiency during pregnancy.

The main change in thyroid function associated with the pregnant state is the requirement of an increased production of thyroid hormone that depends directly upon the adequate availability of dietary iodine and integrity of the glandular machinery. In healthy pregnant women, physiological adaptation takes place when the iodine intake is adequate, while this is replaced by pathological alterations when there is a deficient iodine intake. Pregnancy acts typically, therefore, as a revelator of underlying iodine restriction. Iodine deficiency has important repercussions for both the mother and the fetus, leading to hypothyroxinemia, sustained glandular stimulation and finally goitrogenesis. Furthermore, because severe iodine deficiency may be associated with an impairment in the psychoneurointellectual outcome in the progeny, because both mother and offspring are exposed to iodine deficiency during gestation (and the postnatal period), and because iodine deficiency is still prevalent today in several large regions of the world, iodine supplements should be given systematically to pregnant and breastfeeding mothers. Particular attention is required to ensure that pregnant women receive an adequate iodine supply, in order to reach the ideal recommended nutrient intake of 250 microg iodine/day.

Molecular genetic defects in congenital hypothyroidism.

Recently molecular genetic defects in some cases of congenital hypothyroidism (CH) as well as of rare cases of central hypothyroidism have been identified. These studies have led to the description of so far unexplained forms of these disorders. In some patients with CH early diagnosis by newborn screening and early treatment was not able to lead to a normal mental development. This could subsequently be explained by molecular defects of transcription factors (FOXE-1/FKHL15, NKX2.1) which are important not only for the embryonic development of the thyroid gland but also for other organs including the central nervous system (CNS). These findings will help in understanding the critical role of thyroid hormones in the pre-and postnatal CNS development. However, many questions regarding the molecular defects and their consequences in the majority of patients with CH still remain open and will be addressed in this article.

Early maternal hypothyroxinemia alters histogenesis and cerebral cortex cytoarchitecture of the progeny.

Epidemiological studies from both iodine-sufficient and -deficient human populations strongly suggest that early maternal hypothyroxinemia (i.e., low circulating free thyroxine before onset of fetal thyroid function at midgestation) increases the risk of neurodevelopmental deficits of the fetus, whether or not the mother is clinically hypothyroid. Rat dams on a low iodine intake are hypothyroxinemic without being clinically hypothyroid because, as occurs in pregnant women, their circulating 3,5,3'-triiodothyronine level is usually normal. We studied cell migration and cytoarchitecture in the somatosensory cortex and hippocampus of the 40-day-old progeny of the iodine-deficient dams and found a significant proportion of cells at locations that were aberrant or inappropriate with respect to their birth date. Most of these cells were neurons, as assessed by single- and double-label immunostaining. The cytoarchitecture of the somatosensory cortex and hippocampus was also affected, layering was blurred, and, in the cortex, normal barrels were not formed. We believe that this is the first direct evidence of an alteration in fetal brain histogenesis and cytoarchitecture that could only be related to early maternal hypothyroxinemia. This condition may be 150-200 times more common than congenital hypothyroidism and ought to be prevented both by mass screening of free thyroxine in early pregnancy and by early iodine supplementation to avoid iodine deficiency, however mild.

Feto-maternal repercussions of iodine deficiency during pregnancy. An update.

The main changes in thyroid function associated with the pregnant state are increased thyroid hormone requirements. These increased requirements can only be met by a proportional increase in hormone production, that directly depends upon the availability of dietary iodine. When the iodine intake is adequate, normal "physiological" adaptation takes place. When the intake is restricted, physiological adaptation is progressively replaced by pathological alterations, in parallel with the degree of iodine deprivation, leading to excessive glandular stimulation, hypothyroxinemia, and goiter formation. Thus, pregnancy acts typically as a revelator of underlying iodine restriction and gestation results in an iodine deficient status, even in conditions with only a moderately restricted iodine intake, characteristic of many European regions. Iodine deficiency during pregnancy has important repercussions for both mother and fetus, namely thyroid underfunction and goitrogenesis. Furthermore, iodine deficiency may be associated with alterations of the psychoneuro-intellectual outcome in the progeny. The risk of an abnormal progeny's development is further enhanced because mother and offspring are exposed to iodine deficiency, both during gestation and the postnatal period. Because iodine deficiency is still prevalent in many European regions and remains a subject of great concern, investigators have proposed, since several years, that iodine prophylaxis be introduced systematically during pregnancy, in order to provide mothers with an adequate iodine supply. In areas with a severe iodine deficiency, correcting the iodine lack has proved highly beneficial to prevent mental deficiency disorders. The many actions undertaken to eradicate severe iodine deficiency have allowed to prevent the occurrence of mental retardation in millions young infants throughout the world. In most public health programmes dealing with the correction of iodine deficiency disorders, iodized salt has been used as the preferred strategy in order to convey the iodine supplements to the household. Iodized salt, however, is not the ideal vector in the specific instance of pregnancy (or breastfeeding) or in young infants, because of the necessity to limit salt intake. Hence, particular attention is required in our countries to ensure that pregnant women have an adequate iodine intake, by administering multi-vitamin tablets containing iodide supplements (+125 micro g/d). Finally, it is with some concern that the results of a recent nutritional survey in the USA have disclosed that iodine deficiency, long thought to have been eradicated since many years, may actually show a resurgence, particularly in women in the child-bearing period. This issue needs to be considered seriously by the medical community and public health authorities.

The expression of the sodium/iodide symporter is up-regulated in the thyroid of fetuses of iodine-deficient rats.

Is the fetal thyroid already capable to increase its iodide uptake in response to iodine deficiency? To answer this question, we analyzed the expression of the Na(+)/I(-) symporter and several other genes in the thyroid of rat fetuses at 21 d of gestation from control mothers presenting a mild or more severe iodine deficiency. Female rats were placed on a low iodine diet, not supplemented, or supplemented with iodide or perchlorate for 3 months. The maternal and fetal thyroidal iodide uptake was measured 24 h after injection of 10 microCi Na (125)I into the dams. The absolute iodide uptake of the maternal thyroid was unchanged in a low iodine diet, not supplemented, compared with one supplemented with iodide. In contrast, the fetal thyroid absolute iodide uptake of a low iodine diet, not supplemented, and one supplemented with perchlorate was decreased by 70% and 95% compared with that supplemented with iodide. Na(+)/I(-) symporter mRNA was detected in the fetal thyroid of supplemented with iodide and increased about 2- and 4- fold in the thyroid of fetuses from a low iodine diet, not supplemented, and one supplemented with perchlorate, respectively. Na(+)/I(-) symporter expression was induced in the fetal side of the placenta in both a low iodine diet, not supplemented, and one supplemented with perchlorate; in contrast, Na(+)/I(-) symporter mRNA was never detected in the maternal side of the placenta. Fetal thyroid thyroglobulin and type I deiodinase mRNA contents were only significantly increased with a diet supplemented with perchlorate. Glucose transporter 4 mRNA was decreased in the fetal thyroid of both a low iodine diet, not supplemented, and one supplemented with perchlorate compared with one supplemented with iodide. In conclusion, although the up-regulation of Na(+)/I(-) symporter expression in fetal thyroid and placenta in the low iodine diet, not supplemented group did not lead to restoration of a normal absolute iodide uptake, our data show that all adaptive and/or defending mechanisms against iodine deficiency are already present in the fetus.

Cloning and expression of a novel cysteine-rich secreted protein family member expressed in thyroid and pancreatic mesoderm within the chicken embryo.

We have isolated a new chicken gene that is a member of the cysteine-rich secreted protein family (CRISP). The CRISP family is composed of over 70 members that are found in many phyla of organisms, including: vertebrates, plants, fungi, yeast, and insects. Here we describe the cloning of a novel member of this family, SugarCrisp, and its expression pattern throughout chicken embryogenesis. We also describe its utility as a marker of thyroid and pancreatic mesoderm in the developing chicken embryo and its expression within the human and mouse in glandular tissue.

[The influence of iodine deficiency during pregnancy of fetal and neonatal development]. / Wplyw niedoboru jodu w ciazy na rozwój plodu i noworodka.

The iodine is fundamental substrate for thyroid hormones synthesis. Thyroxine and triiodothyronine play a crucial role in human brain development and maturation. It is well known, that not only fetal, but also maternal thyroid hormones are essential for normal prenatal central nervous system development. During pregnancy complex changes of maternal thyroid function occur and they are influenced by the maternal iodine supply. With decreasing iodine intake, maternal goiter and hypothyroxinemia as well as fetal and neonatal hypothyroidism become more prevalent. The severity of iodine deficiency and hypothyroidism in the mother during early and midgestation is related to the severity of the neural damage in the fetus. In severe iodine deficiency, central nervous system damage is already irreversible at birth and can only be prevented by correction of the maternal iodine deficiency early in pregnancy. Therefore iodine supplementation during pregnancy is now strongly recommended.

Effects of iodine repletion on thyroid morphology in iodine and/or selenium deficient rat term fetuses, pups and mothers.

It has been suggested that selenium deficiency aggravates the iodine-induced thyroid inflammation and necrosis in iodine-deficient Wistar rats and possibly in man. Studies were carried out to determine whether large amounts of iodine given to iodine-deficient pregnant Sprague-Dawley rats with or without selenium deficiency would induce inflammation and necrosis in their term fetal thyroids. Iodine deficiency was induced in the dams by a low iodine diet or perchlorate in the drinking water and iodine excess was achieved by iodinated drinking water during pregnancy or daily subcutaneous injections of iodine from days 20 to 22 of pregnancy, 1 day after perchlorate was discontinued. Studies were also carried out in 30-day-old pups whose nursing mothers were iodine-deficient (perchlorate) with or without selenium deficiency from conception onward. The administration of iodine restored the morphologic changes in the thyroid induced by iodine deficiency, irrespective of selenium status, toward normal without inflammatory changes or necrosis. Possible explanations for these unexpected findings are discussed.

Secretion in milk and transplacental transfer of two iodized oils, Lipiodol UF and Oriodol, in rabbits.

Many countries in the world are inhabited by populations suffering from iodine deficiency. These populations are affected by serious diseases directly related to iodine deficiency. Iodized oil (Lipiodol UF or Oriodol) is routinely used orally or intramuscularly to treat these populations, including pregnant women. The experiments of the present study in gravid or lactating rabbits show that there is transplacental transfer of iodine and secretion of iodine in milk after administration of iodized oil and consequently an accumulation of iodine in the thyroid glands of the mother, the fetus and the neonate. The advantages of treating pregnant women with iodized oil in the populations concerned is thus confirmed. The oral route can be substituted by the intramuscular route.