scholarly journals The Many Faces of Elevated TSH: When to Avoid Thyroid Hormone Therapy in Older Adults

2021 ◽  
Vol 5 (Supplement_1) ◽  
pp. 471-471
Author(s):  
Enoch Abbey ◽  
John McGready ◽  
Luigi Ferrucci ◽  
Eleanor Simonsick ◽  
Jennifer Mammen
Keyword(s):  
Older Adults ◽  
Thyroid Hormone ◽  
Hormone Therapy ◽  
Reference Range ◽  
Target Therapy ◽  
Potential Harm ◽  
Pituitary Thyroid Axis ◽  
Thyroid Axis ◽  
The Many ◽  
Tsh Levels

Abstract We have previously demonstrated that hypothalamic-pituitary-thyroid axis aging is characterized by several distinct patterns. An elevated thyrotropin (TSH) level (mean 5.6mIU/L) with normal free thyroxine (FT4) was present in 75 BLSA participants with at least 3 visits. Twenty-one percent had an historical pattern consistent with primary gland failure, while 13% had a pattern consistent with an HPT response to stressors (aging-adaptation). The remainder had intermediate patterns of change. FT4 >0.92pg/ml identified those in whom TSH elevations occurred with aging-adaptation with a 90.0% sensitivity and 93.8% specificity, indicating no need for therapy. In addition, among 597 participants with stable TSH levels in the reference range, being on thyroid hormone therapy increased mortality risk (IRR=1.8; 95% CI 0.9-2.1). Thus, including FT4 in the diagnostic criteria for hypothyroidism in older adults could target therapy to avoid the potential harm of reversing the aging adaptations in those who do not have true early hypothyroidism.

N-acetyltransferase activity in the Harderian glands of the Syrian hamster, Mesocricetus auratus, is regulated by androgens and by hormones of the pituitary-thyroid axis

1990 ◽  
Vol 127 (1) ◽  
pp. 59-67 ◽  
Author(s):  
G. R. Buzzell ◽  
A. Menendez-Pelaez ◽  
R. A. Hoffman ◽  
M. K. Vaughan ◽  
R. J. Reiter
Keyword(s):  
Thyroid Hormone ◽  
Thyroid Hormones ◽  
Harderian Gland ◽  
Hormone Levels ◽  
Harderian Glands ◽  
Pituitary Thyroid Axis ◽  
Thyroid Axis ◽  
Serum Thyroid Hormone ◽  
Thyroid Hormone Levels ◽  
Tsh Levels

ABSTRACT This study tested the hypothesis that activity of the enzyme N-acetyltransferase (NAT) in the Harderian gland of the Syrian hamster is regulated both by androgens and by hormones of the pituitary-thyroid axis. To test the effects of castration and hypothyroidism, intact or castrated male hamsters were given either tap water or methimazole in their drinking water for 3 weeks. Methimazole suppresses iodination of thyroglobulin, thereby decreasing circulating levels of thyroid hormones and increasing TSH levels. Hypothyroidism or castration caused elevated or depressed Harderian gland NAT activities respectively, compared with euthyroid controls. When castration and hypothyroidism were combined, the animals exhibited high NAT activity compared with castrated euthyroid males. To test the effects of castration and hyperthyroidism, male hamsters were given daily injections of thyroxine (T4) or diluent and were either castrated or left intact for 4 weeks. Intact animals given T4 had depressed Harderian NAT activity; serum thyroid hormone levels were elevated and TSH levels were depressed compared with those of intact controls. Castrated animals had depressed NAT activity below that of intact controls; serum thyroid hormone levels were normal but TSH levels were depressed. Castrated animals given T4 injections had NAT activity similar to that of euthyroid castrated hamsters; thyroid hormone levels were elevated but TSH levels were similar to those seen in euthyroid castrated hamsters. In another experiment, both T4 and tri-iodothyronine (T3) were equally effective in decreasing NAT activity in intact males. To determine the effects of the removal of pituitary influences, male hamsters were hypophysectomized. NAT activity in the Harderian glands of these animals was reduced compared with intact controls. Injection of T4 in hypophysectomized male hamsters did not alter NAT activity from that of hypophysectomized hamsters. Female hamsters given methimazole for 3 weeks had elevated Harderian NAT activity compared with controls. Injection of T4 or T3 for 4 weeks led to significantly reduced Harderian gland NAT activity compared with untreated controls. This response to thyroid hormones was the same, whether T4 or T3 was used. These results can be explained by androgens stimulating Harderian NAT activity, as has been suggested by previous published reports, and by NAT activity being inhibited by thyroid hormones or stimulated by TSH. Journal of Endocrinology (1990) 127, 59–67

scholarly journals Neuropeptide Y1 and Y5 Receptors Mediate the Effects of Neuropeptide Y on the Hypothalamic-Pituitary-Thyroid Axis

Endocrinology ◽  
2002 ◽  
Vol 143 (12) ◽  
pp. 4513-4519 ◽  
Author(s):  
Csaba Fekete ◽  
Sumit Sarkar ◽  
William M. Rand ◽  
John W. Harney ◽  
Charles H. Emerson ◽  
...  
Keyword(s):  
Thyroid Hormone ◽  
Food Intake ◽  
Neuropeptide Y ◽  
Paraventricular Nucleus ◽  
Receptor Agonist ◽  
Pituitary Thyroid Axis ◽  
Thyroid Axis ◽  
Ad Libitum ◽  
Thyroid Hormone Levels ◽  
Hpt Axis

Abstract Neuropeptide Y (NPY) is one of the most important hypothalamic-derived neuropeptides mediating the effects of leptin on energy homeostasis. Central administration of NPY not only markedly stimulates food intake, but simultaneously inhibits the hypothalamic-pituitary-thyroid axis (HPT axis), replicating the central hypothyroid state associated with fasting. To identify the specific NPY receptor subtypes involved in the action of NPY on the HPT axis, we studied the effects of the highly selective Y1 ([Phe7,Pro34]pNPY) and Y5 ([chicken pancreatic polypeptide1–7, NPY19–23, Ala31, Aib32 (aminoisobutyric acid), Q34]human pancreatic polypeptide) receptor agonists on circulating thyroid hormone levels and proTRH mRNA in hypophysiotropic neurons of the hypothalamic paraventricular nucleus. The peptides were administered continuously by osmotic minipump into the cerebrospinal fluid (CSF) over 3 d in ad libitum-fed animals and animals pair-fed to artificial CSF (aCSF)-infused controls. Both Y1 and Y5 receptor agonists nearly doubled food intake compared with that of control animals receiving aCSF, similar to the effect observed for NPY. NPY, Y1, and Y5 receptor agonist administration suppressed circulating levels of thyroid hormones (T3 and T4) and resulted in inappropriately normal or low TSH levels. These alterations were also associated with significant suppression of proTRH mRNA in the paraventricular nucleus, particularly in the Y1 receptor agonist-infused group [aCSF, NPY, Y1, and Y5 (density units ± sem), 97.2 ± 8.6, 39.6 ± 8.4, 19.9 ± 1.9, and 44.6 ± 8.4]. No significant differences in thyroid hormone levels, TSH, or proTRH mRNA were observed between the agonist-infused FSanimals eating ad libitum and the agonist-infused animals pair-fed with vehicle-treated controls. These data confirm the importance of both Y1 and Y5 receptors in the NPY-mediated increase in food consumption and demonstrate that both Y1 and Y5 receptors can mediate the inhibitory effects of NPY on the HPT axis.

Consequences of thyroid hormone deficiency induced by the specific ablation of thyroid follicle cells in adult transgenic mice

1994 ◽  
Vol 143 (1) ◽  
pp. 107-120 ◽  
Author(s):  
H Wallace ◽  
K McLaren ◽  
R Al-Shawi ◽  
J O Bishop
Keyword(s):  
Body Weight ◽  
Thyroid Hormone ◽  
Transgenic Mice ◽  
Follicle Cells ◽  
Hormone Deficiency ◽  
Mrna Levels ◽  
Thyroid Follicle ◽  
Receptor Mrna ◽  
The Many ◽  
Tsh Levels

Abstract The herpes simplex type 1 virus thymidine kinase (HSV1-TK) reporter gene was coupled to a bovine thyroglobulin promoter (TG-tk construct). Within the thyroid glands of transgenic mice expression was confined to thyroid follicle cells. Infusion of Ganciclovir (9-[(1,3-dihydroxy-2-propoxy)methyl]guanine) to 8 to 12 week transgenic females led to the complete loss of thyroid HSV1-TK activity (at 3 to 4 days) and thyroid follicles (between 7 and 14 days). During the first 5 days of treatment a single reciprocal oscillation in circulating thyroxine (T4) and TSH levels occurred. By 14 days the circulating triiodothyronine (T3) and T4 levels of all treated animals were below the detection limits of the assays, while TSH levels were elevated ten-fold and continued to increase thereafter. During 14 days of treatment the thyroids regressed, protein content fell by 80–90% and the C cells, normally dispersed within the central region of each gland, came together in aggregates. Pituitary GH levels in females rose and fell back to normal within 14 days and between 14 and 28 days fell to a level comparable with that of GH-deficient lit/lit mice. The levels of hepatic GH receptor mRNA and the predominant 6·6 kb T3 receptor mRNA were unaffected by thyrocyte ablation. Thyrocyte ablation had no effect on the level of prolactin (Prl) receptor mRNA in females, but increased Prl receptor mRNA levels in males and eliminated group 1 major urinary protein (MUP) mRNA in females. T4 replacement reversed the effects of thyrocyte ablation on MUP mRNA in females and on Prl receptor mRNA in males. Despite the many physiological changes induced by thyrocyte ablation, ablated mice have been maintained for up to 1 year without thyroid hormone supplementation. T4-deficient females were normally fertile and carried pups to term. Although transgenic males expressed HSV1-TK ectopically in spermatids and spermatozoa at levels similar to thyrocyte levels, a rate of Ganciclovir infusion which successfully ablated the thyrocytes did not affect the testis. As an alternative to infusion by minipump, thyrocyte ablation could be achieved by 6 twice-daily injections of Ganciclovir, at a level of 112 μg Ganciclovir/g body weight per day, and fetuses in utero could be thyrocyte ablated by administering 50 or 15 μg/g body weight per day to pregnant females between days 14 and 18 of gestation. These data demonstrate the potential value of transgenic thyrocyte ablation in the study of the effects of thyroid hormone deprivation. Journal of Endocrinology (1994) 143, 107–120

scholarly journals The TRH Gene Is Regulated by Thyroid Hormone at the Level of Transcription in Vivo

2010 ◽  
Vol 31 (1) ◽  
pp. 136-136
Author(s):  
Michelle L. Sugrue ◽  
Kristen R. Vella ◽  
Crystal Morales ◽  
Marisol E. Lopez ◽  
Anthony N. Hollenberg
Keyword(s):  
Thyroid Hormone ◽  
Genomic Region ◽  
Model System ◽  
Model Systems ◽  
In Vivo Model ◽  
Pituitary Thyroid Axis ◽  
Thyroid Axis ◽  
Normal Production

ABSTRACT The expression of the TRH gene in the paraventricular nucleus (PVH) of the hypothalamus is required for the normal production of thyroid hormone (TH) in rodents and humans. In addition, the regulation of TRH mRNA expression by TH, specifically in the PVH, ensures tight control of the set point of the hypothalamic-pituitary-thyroid axis. Although many studies have assumed that the regulation of TRH expression by TH is at the level of transcription, there is little data available to demonstrate this. We used two in vivo model systems to show this. In the first model system, we developed an in situ hybridization (ISH) assay directed against TRH heteronuclear RNA to measure TRH transcription directly in vivo. We show that in the euthyroid state, TRH transcription is present both in the PVH and anterior/lateral hypothalamus. In the hypothyroid state, transcription is activated in the PVH only and can be shut off within 5 h by TH. In the second model system, we employed transgenic mice that express the Cre recombinase under the control of the genomic region containing the TRH gene. Remarkably, TH regulates Cre expression in these mice in the PVH only. Taken together, these data affirm that TH regulates TRH at the level of transcription in the PVH only and that genomic elements surrounding the TRH gene mediate its regulation by T3. Thus, it should be possible to identify the elements within the TRH locus that mediate its regulation by T3 using in vivo approaches.

scholarly journals Minireview: The Neural Regulation of the Hypothalamic-Pituitary-Thyroid Axis

Endocrinology ◽  
2012 ◽  
Vol 153 (9) ◽  
pp. 4128-4135 ◽  
Author(s):  
Ricardo H. Costa-e-Sousa ◽  
Anthony N. Hollenberg
Keyword(s):  
Thyroid Hormone ◽  
Adult Life ◽  
Feedback System ◽  
Primary Hypothyroidism ◽  
Neural Regulation ◽  
Pituitary Thyroid Axis ◽  
Genes Encoding ◽  
Thyroid Axis ◽  
Hpt Axis

Thyroid hormone (TH) signaling plays an important role in development and adult life. Many organisms may have evolved under selective pressure of exogenous TH, suggesting that thyroid hormone signaling is phylogenetically older than the systems that regulate their synthesis. Therefore, the negative feedback system by TH itself was probably the first mechanism of regulation of circulating TH levels. In humans and other vertebrates, it is well known that TH negatively regulates its own production through central actions that modulate the hypothalamic-pituitary-thyroid (HPT) axis. Indeed, primary hypothyroidism leads to the up-regulation of the genes encoding many key players in the HPT axis, such as TRH, type 2 deiodinase (dio2), pyroglutamyl peptidase II (PPII), TRH receptor 1 (TRHR1), and the TSH α- and β-subunits. However, in many physiological circumstances, the activity of the HPT axis is not always a function of circulating TH concentrations. Indeed, circadian changes in the HPT axis activity are not a consequence of oscillation in circulating TH levels. Similarly, during reduced food availability, several components of the HPT axis are down-regulated even in the presence of lower circulating TH levels, suggesting the presence of a regulatory pathway hierarchically higher than the feedback system. This minireview discusses the neural regulation of the HPT axis, focusing on both TH-dependent and -independent pathways and their potential integration.

scholarly journals The Nuclear Receptor Corepressor (NCoR) Controls Thyroid Hormone Sensitivity and the Set Point of the Hypothalamic-Pituitary-Thyroid Axis

2011 ◽  
Vol 25 (2) ◽  
pp. 212-224 ◽  
Author(s):  
Inna Astapova ◽  
Kristen R. Vella ◽  
Preeti Ramadoss ◽  
Kaila A. Holtz ◽  
Benjamin A. Rodwin ◽  
...  
Keyword(s):  
Thyroid Hormone ◽  
Nuclear Receptor ◽  
Hormone Sensitivity ◽  
Set Point ◽  
Nuclear Receptor Corepressor ◽  
Pituitary Thyroid Axis ◽  
Thyroid Axis

scholarly journals The Thyrotropin-Releasing Hormone Gene Is Regulated by Thyroid Hormone at the Level of Transcription in Vivo

Endocrinology ◽  
2010 ◽  
Vol 151 (2) ◽  
pp. 793-801 ◽  
Author(s):  
Michelle L. Sugrue ◽  
Kristen R. Vella ◽  
Crystal Morales ◽  
Marisol E. Lopez ◽  
Anthony N. Hollenberg
Keyword(s):  
Thyroid Hormone ◽  
Genomic Region ◽  
Model System ◽  
Model Systems ◽  
In Vivo Model ◽  
Pituitary Thyroid Axis ◽  
Thyroid Axis ◽  
Normal Production

The expression of the TRH gene in the paraventricular nucleus (PVH) of the hypothalamus is required for the normal production of thyroid hormone (TH) in rodents and humans. In addition, the regulation of TRH mRNA expression by TH, specifically in the PVH, ensures tight control of the set point of the hypothalamic-pituitary-thyroid axis. Although many studies have assumed that the regulation of TRH expression by TH is at the level of transcription, there is little data available to demonstrate this. We used two in vivo model systems to show this. In the first model system, we developed an in situ hybridization (ISH) assay directed against TRH heteronuclear RNA to measure TRH transcription directly in vivo. We show that in the euthyroid state, TRH transcription is present both in the PVH and anterior/lateral hypothalamus. In the hypothyroid state, transcription is activated in the PVH only and can be shut off within 5 h by TH. In the second model system, we employed transgenic mice that express the Cre recombinase under the control of the genomic region containing the TRH gene. Remarkably, TH regulates Cre expression in these mice in the PVH only. Taken together, these data affirm that TH regulates TRH at the level of transcription in the PVH only and that genomic elements surrounding the TRH gene mediate its regulation by T3. Thus, it should be possible to identify the elements within the TRH locus that mediate its regulation by T3 using in vivo approaches.

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