Increase In T4 Levels Research Articles

PO-0357 Prenatal Exposure To Endocrine Disrupting Chemicals (edcs) In Relation To Thyroid Hormone Levels In Infants

Background The presence of chemicals in the environment is ubiquitous. EDCs in particular may disrupt thyroid hormones, which in early life are essential for brain development. As observational studies regarding this topic are still limited, the objective of the current study was to assess the association between prenatal exposure to various EDCs and thyroxine (T4) levels in newborns in a mother-child cohort in the Netherlands. Methods Exposure to amongst others dichlorodiphenyldichloroethylene (DDE), perfluorooctanesulfonic acid (PFOS), and perfluorooctanoic acid (PFOA) was determined in cord plasma or breast milk, and information on T4 levels in heel prick blood spots was obtained through the Dutch neonatal screening programme. Linear regression models were composed for each compound and T4. Models were stratified for gender and adjusted for a priori defined covariates. Results Mean T4 level was 86.9 nmol/L (n = 83). Girls in Q4 of DDE and PFOA exposure showed an increased T4 level compared to Q1, a difference which remained significant in the fully adjusted model (DDE ≥ 110.01 ng/L, +22.2 nmol/L, 95% CI 1.37, 43.04; PFOA ≥ 1201 ng/L, +30.7 nmol/L, 95% CI 13.38, 48.05). In boys a lower T4 level was seen in Q2 for both PFOS and PFOA, however after adjusting the models these associations were attenuated. Conclusion DDE, PFOS and PFOA were associated with T4 in a sex-specific manner. As the study population was relatively small, results should be considered as exploratory. More research is warranted, as studies on the role of exposure to environmental contaminants in thyroid hormone homeostasis are still limited.

Two patients with atypical low triiodothyronine syndrome: primary deiodinase abnormalities?

SummaryLow triiodothyronine (T3) concentrations in the presence of normal thyroxine (T4) and TSH levels, referred to as the low T3 syndrome (LT3S), are common. LT3S may be caused by starvation, various non-thyroidal illnesses (NTIs) and some medications. Reverse T3 (rT3) concentrations are elevated in the more severely ill, and they characteristically fail to respond to exogenous levothyroxine (l-T4) therapy. The biochemical abnormalities have been explained on the basis of altered peripheral deiodinase activities. Herein, we report on two patients with hypothyroid symptoms who on testing were found to have LT3S. They were atypical clinically in not having LT3S due to any of the usual causes, had no increased rT3 concentrations, and had a normal negative TSH feedback response to l-T4. One (patient 1) had previously been diagnosed with Hashimoto's autoimmune primary hypothyroidism and was on l-T4 therapy. Both had T4 concentrations in the reference range. TSH levels were elevated in patient 1 and in the reference range in patient 2. Starting or increasing l-T4 doses resulted in no clinical improvement and no increase in T3 levels in spite of a marked increase in T4 levels. It is suggested that in the absence of the usual causes, lack of elevated rT3 levels, response to treatment and intact negative TSH feedback these two patients differ from the usual secondary causes of decreases in deiodinase activity. It is speculated that they may represent primary alterations in deiodinase enzymes possibly due to genetic variations in the deiodinase-encoding genes.Learning points LT3S is commonly found secondary to starvation, NTIs and use of some medications.Low T3 levels are the result of alterations in the activity of deiodinase enzymes.LT3S without the usual causes may represent a primary disturbance in deiodinase activity.

COMPARATIVE ASPECTS OF MATURATION AND CONTROL OF THYROID HORMONE DEIODINATION DURING DEVELOPMENT

ABSTRACT In all vertebrates the main secretory product of the thyroid gland is thyroxine (T4). The rate of its conversion to the active triiodothyronine (T3) or to the inactive reverse T3 (rT3) can be regulated in the peripheral tissues by deiodination. Probably all vertebrates are capable of both outer and inner ring deiodination (ORD and IRD), catalyzed by deiodinases. Most of these enzymes are related to one of the three mammalian deiodinase types, but the abundance and tissue localization can differ substantially among vertebrate groups. During ontogeny high plasma levels of T3 occur around the period of birth in mammals, of hatching in birds, and of metamorphosis in amphibians. This T3 increase seems to be not only the result of increased T3 production (ORD), but also in considerable degree of decreased T3 degradation (IRD). In fish, birds, and mammals growth hormone can increase plasma T3 levels. In chickens this effect is obtained not by increasing the amount of active hepatic T3-producing (type I)...

Effects of aluminum on the energetic substrates in neotropical freshwater Astyanax bimaculatus (Teleostei: Characidae) females

We investigated the effects of acidic pH and acute aluminum (Al) exposure on the metabolic substrates of Astyanax bimaculatus, and on the ability of these animals to recover in clean water. After an acclimation period, sexually mature A. bimaculatus females were sorted into six glass aquaria with three experimental groups: control in neutral pH (7.0), acidic pH (5.5), and Al (0.5mg·L−1) in acidic pH (5.5). After a 96h treatment, 10 animals from each experimental group were sampled and the rest were returned to clean water in neutral pH without Al for a recovery period of 96h. The acidic pH, either alone or combined with Al, decreased T4 levels, whereas Al exposure increased T3 levels. Recovery of T3 levels occurred after 96h. Al exposure decreased ovary and plasma proteins, muscle glycogen contents, and hepatic lipids due to lipoperoxidation. In the recovery phase, lipids decreased in most tissues, probably to re-establish ovary protein and hepatic glycogen. A. bimaculatus prioritized the use of energetic resources during acclimatization to Al instead of prioritizing reproduction, thereby avoiding the ovulation of impaired eggs.

Triiodothyronin, Thyroxine and Thyrotropin in Vitiligo

Vitiligo is a common pigmentary disorder of the skin, affecting individuals globally. Not only is this ailment psychologically incapacitating, it also has a high incidence of autoimmunity, signifying that its manifestations may be the portrayal of dysfunction of immune system. The aim of this study is to find out the situations of abnormal thyroid function test (TFT) in vitiligo patients. A prospective cross sectional study was conducted at the Dhulikhel Hospital, KUTH, Dhulikhel during November 2008 to January 2011 with the objective to assess the thyroid function tests in vitiligo patients. Total 66 vitiligo patients with male 30 (45%) and female 36 (55%). Total 26 (39.39%) vitiligo patients have been found to have abnormal thyroid function test. Among them 10 had abnormal T3, seven had abnormal T4 and 12 had abnormal TSH level. Thyroid function test were normal in other vitiligo patients. Total seven vitiligo had high level of T3 than normal value, four male and three female. Two had higher level of T4 above 2.0 ng/dl and all were male, while five had abnormally low level of T4 with three male and two female. There were seven vitiligo patient with increased T3 level and three with decreased T3 level, among them six were males and four were females, the age group was ranged from seven to 68 years old. The T4 level were found abnormal in seven vitiligo patients among which five were males and two were females with the age group ranging from 7 to 51 years. There has been significant association of thyroid disorder in the patient with vitiligo. Therefore, patient with vitiligo need to undergo thyroid function test to rule out the thyroid disorder and prevent from long-term complications.

Hormones and breast cancer: can we use them in ways that could reduce the risk?

Many hormones promote or inhibit breast cancer in different ways. These effects and the mechanisms involved are reviewed in order to suggest a potentially safer use of hormones. Natural estrogens, administered transdermally, and natural progesterone may be the safest combination of female hormones. Increased intake of cruciferous vegetables could provide additional safety by improving 2-hydoxyestrone and diminishing 16 alphahydroxyestrone. Testosterone and dehydroepiandrosterone (DHEA) may directly inhibit breast cancer, but could potentially stimulate it by being aromatized into estrogen in the breast. Modest doses with blood level monitoring appear logical. Melatonin and oxytocin are inhibitory to breast and other cancers. Insulin is a growth factor for breast cancer. Managing insulin resistance before the onset of diabetes could reduce the risk. Tri-iodothyronine (T3) has multiple anti-breast cancer effects. Synthroid may not increase T3 levels adequately. Human growth hormone does not appear to increase risk; but it should not be given for performance enhancement.

Thyroid Hormones as Modulators of Immune Activities at the Cellular Level

Increasing evidence suggests that thyroid hormones, L-thyroxine (T(4)) and 3,3',5-triiodo-L-thyronine (T(3)), are modulators of the immune response. In monocytes, macrophages, leukocytes, natural killer cells, and lymphocytes, a wide range of immune functions such as chemotaxis, phagocytosis, generation of reactive oxygen species (ROS), and cytokine synthesis and release are altered under hypo- and hyperthyroid conditions. Hyperthyroidism decreases the proinflammatory activities of monocytes and macrophages, whereas enhancement of phagocytosis and increased levels of ROS may occur during hypothyroidism. The expression of proinflammatory molecules such as macrophage inflammatory protein-1α and interleukin-1β increases in hypothyroidism. However, in Kupffer cells, proinflammatory activities such as the respiratory burst, nitric oxide synthase activity, and tumor necrosis factor-α expression may result from increased T(3) levels. Thyroid hormones also affect natural killer cell activity and cell-mediated immune responses. Still, for many immune cells no clear correlation has been found so far between abnormally high or low T(3) or T(4) levels and the effects observed on the immune responses. In this review we outline the contributions of thyroid hormones to different aspects of innate and adaptive immune responses. The relationship between thyroid hormones and immune cells is complex and T(3) and T(4) may modulate immune responses through both genomic and nongenomic mechanisms. Future studies of the molecular signaling mechanisms involved in this cross-talk between thyroid hormones and the immune system may support development of new strategies to improve clinical immune responses.

Thyroid function in multiple sclerosis.

Thyroid function was studied in 112 MS patients and 175 controls on the basis of T3, T4, T.B.G. and T.S.H. radioimmunoassays. In 33 MS patients with T.R.H. stimulation test was employed additionally. The MS patients had significantly increased T4 levels whereas T3 and T.S.H. were found to be significantly lower. No differences were found in the T.R.H.- stimulated T.S.H. response. The changes in thyroid function parameters were similar in different courses of MS and did not correlate with the degree of clinical disability. The results suggest that in MS the T4/T3 conversion might be reduced as seen in acute or chronic diseases. X

Hormones and breast cancer: can we use them in ways that could reduce the risk?

Many hormones promote or inhibit breast cancer in different ways. These effects and the mechanisms involved are reviewed in order to suggest a potentially safer use of hormones. Natural estrogens, administered transdermally, and natural progesterone may be the safest combination of female hormones. Increased intake of cruciferous vegetables could provide additional safety by improving 2-hydoxyestrone and diminishing 16 alphahydroxyestrone. Testosterone and dehydroepiandrosterone (DHEA) may directly inhibit breast cancer, but could potentially stimulate it by being aromatized into estrogen in the breast. Modest doses with blood level monitoring appear logical. Melatonin and oxytocin are inhibitory to breast and other cancers. Insulin is a growth factor for breast cancer. Managing insulin resistance before the onset of diabetes could reduce the risk. Tri-iodothyronine (T3) has multiple anti-breast cancer effects. Synthroid may not increase T3 levels adequately. Human growth hormone does not appear to increase risk; but it should not be given for performance enhancement.

Endocrine effects of tetrabromobisphenol-A (TBBPA) in Wistar rats as tested in a one-generation reproduction study and a subacute toxicity study

Endocrine effects of the brominated flame retardant tetrabromobisphenol-A (TBBPA) were studied in a one-generation reproduction assay in Wistar rats via repeated dietary exposure, applying eight dose groups at 0–3–10–30–100–300–1000–3000 mg/kg body weight/day (mkd). This design enables dose–response analysis and calculation of benchmark doses (BMDL). This reproduction study was preceded by a 28-day repeat dose subacute toxicity study, at 0–30–100–300 mkd. Major effects in the reproduction study included decreased circulating thyroxine (T4) with BMDLs of 31 (m) and 16 (f) mkd, and increased weight of testis and male pituitary (BMDLs of 0.5 and 0.6 mkd). The hypothyroxinemia correlated to a cluster of developmental parameters including delayed sexual development in females, decreased pup mortality, and effects on brainstem auditory evoked potentials [Lilienthal, H., Verwer, C.M., Van der Ven, L.T.M., Piersma, A.H., Vos, J.G., 2008. Neurobehavioral effects of tetrabromobisphenol A (TBBPA) in rats after pre- and postnatal exposure. Toxicology]. A second cluster of parameters in F1 animals was correlated to increased testis weight, and included female gonad weight, endometrium height, CYP19/aromatase activity in the ovary, and plasma testosterone levels in males. These two correlation clusters suggest a dual action of TBBPA. The only effects in the subacute study were decreased circulating T4 and increased T3 levels in males (BMDLs 48 and 124 mkd), and non-significant trends for these parameters in females, suggesting that the other effects in the reproduction study were induced during development. Combined with data of human exposure to environmental TBBPA, the margin of exposure for highly exposed populations can be calculated at 2.6, and current use of TBBPA may therefore be a matter of concern for human health.

Efeitos da espironolactona sobre as alterações miocárdicas induzidas pelo hormônio tireoideano em ratos

To study the possible role of aldosterone on thyroid hormone-induced myocardium hypertrophy, using spironolactone. To evaluate morphological changes in the myocardium induced by thyroid hormone and the possible effects of spironolactone use on these alterations. Forty Wistar rats were studied. The animals were allocated to four groups and were given: the vehicle used for dilution of the thyroid hormone (C); sodium levothyroxin at 50 microg/rat/day (H); spironolactone, 0.3 mg/kg/day (S); or thyroid hormone plus spironolactone (HS), at the same doses mentioned above, for 28 consecutive days. All the animals were weighed, had blood drawn for hormonal measurements and underwent ECG at the start and the end of the experiment. At the end of experiment all animals were euthanized, the weight of the left ventricle (LV) was determined and LV slices were obtained for morphological analysis. There was an increase in T3 levels, decrease of body weight and higher heart rate in the animals from group H. The LV weight was significantly higher in the H e HS groups. The histometric analyses that measured the diameter of the myocytes showed higher values in group H and a progressive decrease in groups HS, S and C, with a significant difference among all the groups. The addition of spironolactone decreased the transversal myocyte hypertrophy by 14.6%. Rats treated with thyroid hormone present cardiac hypertrophy with increased LV weight and greater myocyte diameter. Spironolactone, when associated with thyroid hormone, can partially prevent this hypertrophy through mechanisms that are yet to be determined.

Effects of Feed Restriction and Dietary Fat Saturation on Performance and Serum Thyroid Hormones of Broiler Chickens

This experiment carried out to study the effects of dietary fat saturation on performance and serum thyroid hormones of broilers under free or skip a day nutrition at 18-28 days of age. We used 720 male Ross 308 broiler chickens in a completely randomized design with a 2*4 factorial arrangement with 3 replicate and 30 chicks for each replicate. Experiment factors were: 1skip a day or free feeding at days 10-28 of age and, 2diets with different unsaturated to saturated fatty acid ratios (2, 3.5, 5 and 6.5) formulated using different levels of sunflower oil and tallow. At 28 and 42 days of age, weight gain and feed consumption recorded and blood samples were taken. SAS software used for Variance analysis and means comparing. Skip a day nutrition at days 18-28 of age significantly reduced feed intake and weight gain and increased feed conversion, But free nutrition at days 29-42 of age removed this differences. At day 28, diet with unsaturated to saturated ratio of 6.5 significantly reduced feed intake and weight gain and increased feed conversion. At day 42 of age dietary fat type didn’t have any significant effect on feed intake and weight gain but altered feed conversion as a manner same to day 28 of age. Skip a day nutrition significantly decreased T3 and increased T4 levels at day 28 of age but this effects were disappeared after re-feeding at day 42 of age. This survey showed that feed restriction didn’t affect bird’s ability to utilize fats with different degrees of saturation. Fat type and feed restriction affect broilers performance separately without any interaction. Dietary fat saturation didn’t have any significant effect on serum thyroid hormones levels, while feed restriction have a pronounce effect.

「環境と健康」研究における最前線 化学物質と健康―胎仔期および授乳期ダイオキシン曝露によるラット甲状腺過形成とその毒性メカニズム―

Effects of gestational and lactational exposure to 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin (TCDD) on pup thyroids were investigated in the rat. Pregnant Holtzman rats, TCDD-sensitive strain, were given a single oral dose of 200ng or 800ng TCDD/kg on gestational day (GD) 15. Parameters related to the thyroid functions were examined on postnatal days (PNDs) 21 and 49. Thyroxin (T4) levels in pup serum were decreased significantly on PND21 in the TCDD-exposed groups, but a significant increase in T4 levels were found on PND49 in the higher dose group. The serum levels of thyroid stimulating hormone (TSH) was more than 2-fold higher in male offspring as compared to the control on PNDs 21 and 49 at the higher dose of TCDD (800ng/kg). A significant induction of UDP-glucuronosyltransferase-1 (UGT1) gene by TCDD was observed on PND 21, but returned to basal levels on PND 49. Gene expression of cytochrome P4501A1 (CYP1A1) was markedly induced in the liver treated with TCDD. A single oral exposure to TCDD (800ng/kg) during perinatal period resulted in hyperplasia of the thyroid gland of pups on PND 49. This was confirmed by proliferating cell nuclear antigen (PCNA) immunocytochemistry. We thus conclude that gestational and lactational exposure to TCDD disrupts thyroid hormone homeostasis, which results in a sustained excessive secretion of TSH, leading to the hyperplasia of thyroid follicular cells.

Tissue Deiodinase Activity during Prolonged Critical Illness: Effects of Exogenous Thyrotropin-Releasing Hormone and Its Combination with Growth Hormone-Releasing Peptide-2

Prolonged critical illness is characterized by reduced pulsatile TSH secretion, causing reduced thyroid hormone release and profound changes in thyroid hormone metabolism, resulting in low circulating T(3) and elevated rT(3) levels. To further unravel the underlying mechanisms, we investigated the effects of exogenous TRH and GH-releasing peptide-2 (GHRP-2) in an in vivo model of prolonged critical illness. Burn-injured, parenterally fed rabbits were randomized to receive 4-d treatment with saline, 60 microg/kg.h GHRP-2, 60 microg/kg.h TRH, or 60 microg/kg.h TRH plus 60 microg/kg.h GHRP-2 started on d 4 of the illness (n = 8/group). The activities of the deiodinase 1 (D1), D2, and D3 in snap-frozen liver, kidney, and muscle as well as their impact on circulating thyroid hormone levels were studied. Compared with healthy controls, hepatic D1 activity in the saline-treated, ill animals was significantly down-regulated (P = 0.02), and D3 activity tended to be up-regulated (P = 0.06). Infusion of TRH and TRH plus GHRP-2 restored the catalytic activity of D1 (P = 0.02) and increased T(3) levels back within physiological range (P = 0.008). D3 activity was normalized by all three interventions, but only addition of GHRP-2 to TRH prevented the rise in rT(3) seen with TRH alone (P = 0.02). Liver D1 and D3 activity were correlated (respectively, positively and negatively) with the changes in circulating T(3) (r = 0.84 and r = -0.65) and the T(3)/rT(3) ratio (r = 0.71 and r = -0.60). We conclude that D1 activity during critical illness is suppressed and related to the alterations within the thyrotropic axis, whereas D3 activity tends to be increased and under the joint control of the somatotropic and thyrotropic axes.

Empenamento, níveis hormonais de triiodotironina e tiroxina e temperatura corporal de frangos de corte de diferentes genótipos criados em diferentes condições de temperatura

Estudou-se o empenamento, os níveis hormonais de Triiodotironina (T3) e Tiroxina (T4) e a temperatura corporal de frangos criados em diferentes temperaturas. Foram alojados 180 pintainhos Cobb 500 e 180 pintainhos ISA Label JA57, em temperaturas termoneutra, quente ou fria. O delineamento utilizado foi inteiramente ao acaso, em modelo fatorial 2 x 3 (2 linhagens e 3 temperaturas) com 8 repetições. Houve um aumento das concentrações de T3, nas aves criadas no frio, e uma redução no calor. Também no calor, os frangos ISA Label apresentaram níveis mais altos de T4. As aves Cobb apresentaram uma redução de T4 no calor ou no frio aos 42 dias e no calor aos 21 dias de idade. Houve menor empenamento aos 42 dias, quando os frangos foram criados em alta temperatura e um menor empenamento das aves ISA Label, quando comparadas aos frangos Cobb. As aves criadas no calor apresentaram maior temperatura corporal. Os frangos Cobb apresentaram um aumento na sua temperatura interna, quando criados em ambiente quente. Já os frangos da linhagem ISA Label mantiveram sua temperatura interna, independentemente da temperatura ambiente. É possível concluir que a temperatura ambiente afeta o empenamento dos frangos de corte de linhagens de rápido ganho de peso, que também apresentaram menor tolerância ao calor, demonstrada através de uma maior temperatura corporal e temperatura interna.

Thyroid hormone and prolactin profiles in male and female turkeys following photostimulation

The turkey hen, a photosensitive bird, will become photorefractory (PR) during the reproductive cycle and will cease laying despite a stimulatory day length. This response is thought to be “programmed” by hormonal events early in the reproductive cycle. The turkey tom, in contrast, produces semen for extended periods and has not been shown to exhibit PR. We compared hormone profiles following photostimulation of hens and toms to assess differences that might program one, but not the other, for PR. We photostimulated with 16 h light per day and measured plasma prolactin (PRL), thyroxine (T4), and triiodothyronine (T3) weekly for 12 wk, and again at 16 and 22 wk. Hens were fed ad libitum, and toms were moderately feed-restricted. Results showed increasing PRL levels following photostimulation in hens, with peak levels occurring at about the time of peak egg production, and declining thereafter. Toms maintained significantly lower concentrations of PRL (P < 0.0001) than hens after 2 wk of photostimulation. A highly significant sex by time interaction in plasma T3 levels was observed due to extreme fluctuations in males. Similar, often reciprocal, fluctuations in mean T4 concentrations also occurred in males. We recycled the toms and repeated blood collections under identical conditions, but with ad libitum feeding to determine if feed restriction may have produced these unusual results. This study revealed an initial significant decline in plasma T3 levels and an increase in T4 levels immediately following photostimulation, and then steady (T4) or slowly rising (T3) levels through 12 wk photostimulation. We conclude that PRL profiles of toms and hens differ markedly during the reproductive cycle, lending support to the suggestion that rising PRL may mediate the onset of PR. Further study is needed to determine if the low plasma T3 levels in males may be related to delayed PR. The extreme fluctuations in plasma T3 and T4 levels of toms receiving relatively mild feed restriction suggest a need for further study of the metabolic effects of feed restriction in turkeys.

Efeito da temperatura ambiente sobre hormônios tireoideanos, temperatura corporal e empenamento de frangos de corte, fêmeas, de diferentes genótipos

Three hundred and sixty female broilers, Cobb – 500 and ISA – Label JA 57 were raised under cold, neutral and hot temperatures in a complete randomized design with 3 x 2 factorial scheme (3 temperatures and 2 strains), with 8 repetitions to evaluate plasmatic levels of Thyroxyne (T4) and Triiodothyronine (T3), body temperature and feathering birds. On hot temperature there was a decrease in T3 levels at 21, 35 and 42 days old and an increase in T4 levels at 21 days old. There was a decrease in the total feathering, in chest, wings and abdomen and an increase in superficial and body temperature. Female broilers ISA Label had better feathering, however lowest superficial temperature, average superficial temperature and body temperature. Environmental temperature affects the feathering of fast growing female broilers, that have low hot tolerance shown through the biggest body temperature. Hormonal levels of T3 and T4 were affected by environmental temperature

Changes in olfactory inputs modify the energy balance response to short days in male gray mouse lemurs

The role of olfaction/olfactory cues on photoperiodic responses was assessed in Malagasy primate, the gray mouse lemur. When exposed to short photoperiod (SP), this primate demonstrates rapid changes in energy balance as adaptive anticipatory response for winter survival. To follow early changes induced by SP exposure, body mass, food intake, resting metabolism (RMR) and free thyroxin levels in plasma (T4) were measured in males abruptly transferred to SP: six intact males (controls), eight males that underwent bilateral olfactory removal (BOX) and eight males exposed to male urinary cues (U-exposed). To assess the effect of SP exposure, two other groups were maintained for 6 weeks under LP: six controls and six BOX males. Whereas all studied parameters remained constant in controls and BOX males maintained under LP, exposure to SP led to different responses according to groups. In controls, SP exposure led to a regular increase in body mass and after 4 weeks under SP, plasma T4 levels, food consumption and RMR significantly decreased. Even if BOX males demonstrated hyperphagic patterns regardless of the photoperiod, an increase in body mass was also induced by SP exposure but without changes in RMR or food intake that were body mass-dependent. In U-exposed males, body mass gain was significantly reduced while food intake and RMR remained high. In both BOX and U-exposed males, SP exposure led to a transient but high increase in T4 levels compared to controls. These results suggest that olfaction/olfactory cues may delay the SP-mediated changes in energy balance.

Brain Data Reveal Why Psychotherapy Works

Brain Data Reveal Why Psychotherapy Works

Nutrition, evolution and thyroid hormone levels – a link to iodine deficiency disorders?

An increased iodine requirement as a result of significant changes in human nutrition rather than a decreased environmental iodine supply is suggested to represent the main cause of the iodine deficiency disorders (IDD). The pathomechanism proposed is based on the fact that serum concentrations of thyroid hormones, especially of trijodothyronine (T3), are dependent on the amount of dietary carbohydrate. High-carbohydrate diets are associated with significantly higher serum T3 concentrations, compared with very low-carbohydrate diets. While our Paleolithic ancestors subsisted on a very low carbohydrate/high protein diet, the agricultural revolution about 10,000 years ago brought about a significant increase in dietary carbohydrate. These nutritional changes have increased T3 levels significantly. Higher T3 levels are associated with an enhanced T3 production and an increased iodine requirement. The higher iodine requirement exceeds the availability of iodine from environmental sources in many regions of the world, resulting in the development of IDD.