scholarly journals Thyroid hormones and seasonal reproductive neuroendocrine interactions

Reproduction ◽  
2008 ◽  
Vol 136 (1) ◽  
pp. 1-8 ◽  
Author(s):  
Nobuhiro Nakao ◽  
Hiroko Ono ◽  
Takashi Yoshimura
Keyword(s):  
Thyroid Hormone ◽  
Thyroid Hormones ◽  
Biological Process ◽  
Critical Role ◽  
Day Length ◽  
Seasonal Reproduction ◽  
Seasonal Breeding ◽  
Length Changes ◽  
Neuroendocrine Axis ◽  
The Brain

Many animals that breed seasonally measure the day length (photoperiod) and use these measurements as predictive information to prepare themselves for annual breeding. For several decades, thyroid hormones have been known to be involved in this biological process; however, their precise roles remain unknown. Recent molecular analyses have revealed that local thyroid hormone activation in the hypothalamus plays a critical role in the regulation of the neuroendocrine axis involved in seasonal reproduction in both birds and mammals. Furthermore, functional genomics analyses have revealed a novel function of the hormone thyrotropin. This hormone plays a key role in signaling day-length changes to the brain and thus triggers seasonal breeding. This review aims to summarize the currently available knowledge on the interactions between elements of the thyroid hormone axis and the neuroendocrine system involved in seasonal reproduction.

Thyroid hormones regulate phosphate homoeostasis through transcriptional control of the renal type IIa sodium-dependent phosphate co-transporter (Npt2a) gene

2010 ◽  
Vol 427 (1) ◽  
pp. 161-169 ◽  
Author(s):  
Mariko Ishiguro ◽  
Hironori Yamamoto ◽  
Masashi Masuda ◽  
Mina Kozai ◽  
Yuichiro Takei ◽  
...  
Keyword(s):  
Thyroid Hormone ◽  
Thyroid Hormones ◽  
Molecular Mechanisms ◽  
Hormone Receptors ◽  
Critical Role ◽  
Serum Phosphate ◽  
Luciferase Assay ◽  
Mobility Shift ◽  
Intron 1 ◽  
Sodium Dependent

The type IIa renal sodium-dependent phosphate (Na/Pi) co-transporter Npt2a is implicated in the control of serum phosphate levels. It has been demonstrated previously that renal Npt2a protein and its mRNA expression are both up-regulated by the thyroid hormone T3 (3,3′,5-tri-iodothyronine) in rats. However, it has never been established whether the induction was mediated by a direct effect of thyroid hormones on the Npt2a promoter. To address the role of Npt2a in T3-dependent regulation of phosphate homoeostasis and to identify the molecular mechanisms by which thyroid hormones modulate Npt2a gene expression, mice were rendered pharmacologically hypo- and hyper-thyroid. Hypothyroid mice showed low levels of serum phosphate and a marked decrease in renal Npt2a protein abundance. Importantly, we also showed that Npt2a-deficient mice had impaired serum phosphate responsiveness to T3 compared with wild-type mice. Promoter analysis with a luciferase assay revealed that the transcriptional activity of a reporter gene containing the Npt2a promoter and intron 1 was dependent upon TRs (thyroid hormone receptors) and specifically increased by T3 in renal cells. Deletion analysis and EMSAs (electrophoretic mobility-shift assays) determined that there were unique TREs (thyroid-hormone-responsive elements) within intron 1 of the Npt2a gene. These results suggest that Npt2a plays a critical role as a T3-target gene, to control phosphate homoeostasis, and that T3 transcriptionally activates the Npt2a gene via TRs in a renal cell-specific manner.

scholarly journals Bone Microarchitectural Changes in Hyperthyroid Women Compared to a Normal Canadian Cohort

2021 ◽  
Vol 5 (Supplement_1) ◽  
pp. A256-A257
Author(s):  
Terra G Arnason ◽  
David Cooper ◽  
Reza Behdani ◽  
Saija Kontulainen
Keyword(s):  
Thyroid Hormone ◽  
Thyroid Hormones ◽  
Fracture Risk ◽  
Trabecular Bone ◽  
Bone Microarchitecture ◽  
Critical Role ◽  
Primary Objective ◽  
Mineral Density ◽  
Tsh Suppression ◽  
Increased Risk

Abstract Thyroid hormones play a critical role in bone physiology during childhood, but also impacts adult bone metabolism. Hyperthyroidism promotes accelerated bone turnover and bone remodelling which is associated with net loss of bone mineral density over time (BMD) and these changes have been quantitated using the gold standard of measuring BMD, Dual Energy X-ray Absorptiometry (DEXA). Ordinarily, biochemical thyroid hormone normalization restores BMD towards normal, yet an increased risk of fractures remains lifelong. DEXA, therefore, cannot explain the underlying etiology for fracture risk which may be due to undetected changes in bone microarchitecture. Our primary objective was to utilize an investigational 3-dimensional bone imaging technology, High Resolution peripheral Quantitative Tomography (HR-pQCT), to study bone microarchitecture in actively hyperthyroid women to determine if there are changes in cortical and trabecular bone microarchitecture from that of age-matched controls. A subset of women were rescanned using HR-pCT after thyroid hormones had been normalized for at least 6 months to determine if there were cortical/trabecular architectural changes that reversed towards normal in these individual cases. We enrolled 20 hyperthyroid women (age 20–76) for this pilot study who had persistent TSH suppression for >3 months (TSH< 0.5, normal range: 0.5–4.49 mU/L) without secondary causes for bone loss. Their etiology was divided amongst TSH suppression for thyroid carcinoma, Grave’s disease and iatrogenic hyperthyroidism. HR-pQCT scans of the radius were compared to age-matched scans of normal females, available from the robust Canadian Multicentre Osteoporosis Study (CaMOS) control cohort. Four participants were re-scanned after 6 months of TSH normalization to assess reversibility. The observed data showed statistically significant differences in key parameters of bone microarchitecture in hyperthyroidism, independent of etiology. We observed decreased cortical thickness and increased failure load as statistically different from age-matched controls. Increases in cortical bone porosity and decreases in volumetric bone density (cortical, trabecular and total) were notable but did not reach significance in this small study. Repeat scans following normalization of thyroid hormone levels revealed consistent (partial, nonsignificant) normalization of multiple bone microarchitecture elements including increased trabecular number/thickness, and decreased cortical porosity. These findings suggest that there are changes in both cortical and trabecular bone during active hyperthyroidism that may contribute to increased lifelong fracture risk.

scholarly journals Molecular basis for regulating seasonal reproduction in vertebrates

2016 ◽  
Vol 229 (3) ◽  
pp. R117-R127 ◽  
Author(s):  
Taeko Nishiwaki-Ohkawa ◽  
Takashi Yoshimura
Keyword(s):  
Thyroid Hormone ◽  
Pituitary Gland ◽  
Environmental Changes ◽  
Thyroid Stimulating Hormone ◽  
Day Length ◽  
Adaptive Behaviors ◽  
Seasonal Reproduction ◽  
Pars Tuberalis ◽  
Light Detection ◽  
Stimulating Hormone

Animals that inhabit mid- to high-latitude regions exhibit various adaptive behaviors, such as migration, reproduction, molting and hibernation in response to seasonal cues. These adaptive behaviors are tightly regulated by seasonal changes in photoperiod, the relative day length vs night length. Recently, the regulatory pathway of seasonal reproduction has been elucidated using quail. In birds, deep brain photoreceptors receive and transmit light information to the pars tuberalis in the pituitary gland, which induces the secretion of thyroid-stimulating hormone. Thyroid-stimulating hormone locally activates thyroid hormone via induction of type 2 deiodinase in the mediobasal hypothalamus. Thyroid hormone then induces morphological changes in the terminals of neurons that express gonadotropin-releasing hormone and facilitates gonadotropin secretion from the pituitary gland. In mammals, light information is received by photoreceptors in the retina and neurally transmitted to the pineal gland, where it inhibits the synthesis and secretion of melatonin, which is crucial for seasonal reproduction. Importantly, the signaling pathway downstream of light detection and signaling is fully conserved between mammals and birds. In fish, the regulatory components of seasonal reproduction are integrated, from light detection to neuroendocrine output, in a fish-specific organ called the saccus vasculosus. Various physiological processes in humans are also influenced by seasonal environmental changes. The findings discussed herein may provide clues to addressing human diseases, such as seasonal affective disorder.

scholarly journals Transport of thyroid hormones via the choroid plexus into the brain: the roles of transthyretin and thyroid hormone transmembrane transporters

2015 ◽  
Vol 9 ◽  
Author(s):  
Samantha J. Richardson ◽  
Roshen C. Wijayagunaratne ◽  
Damian G. D'Souza ◽  
Veerle M. Darras ◽  
Stijn L. J. Van Herck
Keyword(s):  
Thyroid Hormone ◽  
Thyroid Hormones ◽  
Choroid Plexus ◽  
Transmembrane Transporters ◽  
The Brain

scholarly journals Testicular Growth and Regression Are Not Correlated With Dio2 Expression in a Wild Male Songbird, Sturnus vulgaris, Exposed to Natural Changes in Photoperiod

Endocrinology ◽  
2013 ◽  
Vol 154 (5) ◽  
pp. 1813-1819 ◽  
Author(s):  
George E. Bentley ◽  
Shanna Tucker ◽  
Heather Chou ◽  
Michaela Hau ◽  
Nicole Perfito
Keyword(s):  
Wild Species ◽  
Day Length ◽  
Seasonal Breeding ◽  
Reproductive Seasonality ◽  
Iodothyronine Deiodinase ◽  
Long Day ◽  
Founder Populations ◽  
Acute Changes ◽  
The Brain

Abstract Timing of seasonal breeding in birds and mammals is regulated by changing the day length and is dependent on the presence of thyroid hormones. A mechanism for thyroid-dependent control of seasonality has been proposed, in which exposure to long day lengths induces rapid local conversion of T4 to its bioactive form, T3, via the up-regulation of the enzyme type 2 iodothyronine deiodinase (Dio2) in the brain, and the down-regulation of Dio3 (which inactivates T3). Such changes were correlated with gonadotropin release and gonadal growth in quail. This mechanism was elucidated in a domesticated species (quail) exposed to unnatural acute changes in day length. Here we investigated the Dio2/Dio3 mechanism in a wild species, the European starling, under naturally changing day length. Although Dio2 expression varied seasonally, Dio3 did not. We found no correlation of Dio2 with photoperiod, seasonal regulation of GnRH, or testicular volume. The observed differences in data from starlings and quail could be a result of phylogeny, genetic drift from founder populations, or differences in reproductive seasonality in addition to or instead of arising from domestication or use of artificially changing photoperiods. Overall, the data indicate that in a wild species exposed to natural changes in day length, the current proposed mechanism for photoperiodic timing is less straightforward than is generally accepted and might not be as universally applicable as previously thought.

scholarly journals Molecular Genetic Understanding of Photoperiodic Regulation of Flowering Time in Arabidopsis and Soybean

2021 ◽  
Vol 23 (1) ◽  
pp. 466
Author(s):  
Xiao Luo ◽  
Mengnan Yin ◽  
Yuehui He
Keyword(s):  
Flowering Time ◽  
Molecular Mechanisms ◽  
Molecular Genetic ◽  
Critical Role ◽  
Day Length ◽  
Long Day ◽  
Photoperiodic Regulation ◽  
Length Changes ◽  
Developmental Switch ◽  
Photoperiod Control

The developmental switch from a vegetative phase to reproduction (flowering) is essential for reproduction success in flowering plants, and the timing of the floral transition is regulated by various environmental factors, among which seasonal day-length changes play a critical role to induce flowering at a season favorable for seed production. The photoperiod pathways are well known to regulate flowering time in diverse plants. Here, we summarize recent progresses on molecular mechanisms underlying the photoperiod control of flowering in the long-day plant Arabidopsis as well as the short-day plant soybean; furthermore, the conservation and diversification of photoperiodic regulation of flowering in these two species are discussed.

Establishment of Early Pregnancy Related Thyroid Hormone Models and Reference Intervals for Pregnant Women in China Based on Real World Data

2021 ◽  
Vol 53 (04) ◽  
pp. 272-279
Author(s):  
Chaochao Ma ◽  
Xiaoqi Li ◽  
Lixin Liu ◽  
Xinqi Cheng ◽  
Fang Xue ◽  
...  
Keyword(s):  
Thyroid Hormone ◽  
Thyroid Hormones ◽  
Pregnant Women ◽  
Early Pregnancy ◽  
Gestational Age ◽  
Dynamic Change ◽  
Reference Intervals ◽  
Thyroid Stimulating Hormone ◽  
Free Thyroxine ◽  
Stimulating Hormone

AbstractThyroid hormone reference intervals are crucial for diagnosing and monitoring thyroid dysfunction during early pregnancy, and the dynamic change trend of thyroid hormones during pregnancy can assist clinicians to assess the thyroid function of pregnant women. This study aims to establish early pregnancy related thyroid hormones models and reference intervals for pregnant women. We established two derived databases: derived database* and derived database#. Reference individuals in database* were used to establish gestational age-specific reference intervals for thyroid hormones and early pregnancy related thyroid hormones models for pregnant women. Individuals in database# were apparently healthy non-pregnant women. The thyroid hormones levels of individuals in database# were compared with that of individuals in database* using nonparametric methods and the comparative confidence interval method. The differences in thyroid stimulating hormone and free thyroxine between early pregnant and non-pregnant women were statistically significant (p<0.0001). The reference intervals of thyroid stimulating hormone, free thyroxine and free triiodothyronine for early pregnant women were 0.052–3.393 μIU/ml, 1.01–1.54 ng/dl, and 2.51–3.66 pg/ml, respectively. Results concerning thyroid stimulating hormone and free thyroxine reference intervals of early pregnancy are comparable with those from other studies using the same detection platform. Early pregnancy related thyroid hormones models showed various change patterns with gestational age for thyroid hormones. Early pregnancy related thyroid hormones models and reference intervals for pregnant women were established, so as to provide accurate and reliable reference basis for the diagnosing and monitoring of maternal thyroid disfunction in early pregnancy.

scholarly journals Blood Micronutrient and Thyroid Hormone Concentrations in the Oldest-Old

2000 ◽  
Vol 85 (6) ◽  
pp. 2260-2265 ◽  
Author(s):  
Giovanni Ravaglia ◽  
Paola Forti ◽  
Fabiola Maioli ◽  
Barbara Nesi ◽  
Loredana Pratelli ◽  
...  
Keyword(s):  
Thyroid Hormone ◽  
Thyroid Hormones ◽  
Oldest Old ◽  
Serum Zinc ◽  
Blood Levels ◽  
Elderly Age ◽  
Blood Concentrations ◽  
Significant Difference ◽  
Plasma Retinol ◽  
Age Range

Several micronutrients are involved in thyroid hormone metabolism, but it is unclear whether their marginal deficits may contribute to the alterations in thyroid function observed in extreme aging. The relationships among blood concentrations of thyroid hormones and selenium, zinc, retinol, and α-tocopherol were studied in 44 healthy Northern Italian oldest-old subjects (age range, 90–107 yr), selected by the criteria of the SENIEUR protocol. Control groups included 44 healthy adult (age range, 20–65 yr) and 44 SENIEUR elderly (age range, 65–89 yr) subjects. Oldest-old subjects had higher TSH (P &lt; 0.01) and lower free T3 (FT3)/freeT4 (FT4) ratio, zinc, and selenium serum values (P &lt; 0.001) than adult and elderly control subjects. No significant difference was found for plasma retinol and α-tocopherol values. The associations between micronutrients and thyroid hormones were evaluated by multivariate analysis. In oldest-old subjects, plasma retinol was negatively associated with FT4 (P = 0.019) and TSH serum levels (P = 0.040), whereas serum zinc was positively associated with serum FT3 (P = 0.010) and FT3/FT4 ratio (P = 0.011). In younger subjects, no significant association was found among thyroid variables and micronutrients. In conclusion, blood levels of specific micronutrients are associated with serum iodothyronine levels in extreme aging.

scholarly journals Reactive Oxygen Species: Beyond Their Reactive Behavior

2021 ◽  
Vol 46 (1) ◽  
pp. 77-87
Author(s):  
Arnaud Tauffenberger ◽  
Pierre J. Magistretti
Keyword(s):  
Reactive Oxygen Species ◽  
Second Messengers ◽  
Critical Role ◽  
Complex Function ◽  
Reactive Oxygen ◽  
High Reactivity ◽  
Oxygen Species ◽  
Health And Disease ◽  
Cellular Dysfunction ◽  
The Brain

AbstractCellular homeostasis plays a critical role in how an organism will develop and age. Disruption of this fragile equilibrium is often associated with health degradation and ultimately, death. Reactive oxygen species (ROS) have been closely associated with health decline and neurological disorders, such as Alzheimer’s disease or Parkinson’s disease. ROS were first identified as by-products of the cellular activity, mainly mitochondrial respiration, and their high reactivity is linked to a disruption of macromolecules such as proteins, lipids and DNA. More recent research suggests more complex function of ROS, reaching far beyond the cellular dysfunction. ROS are active actors in most of the signaling cascades involved in cell development, proliferation and survival, constituting important second messengers. In the brain, their impact on neurons and astrocytes has been associated with synaptic plasticity and neuron survival. This review provides an overview of ROS function in cell signaling in the context of aging and degeneration in the brain and guarding the fragile balance between health and disease.

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