The log <scp>TSH</scp>–free T4 relationship in a community‐based cohort is nonlinear and is influenced by age, smoking and thyroid peroxidase antibody status

Brown, Suzanne J.; Bremner, Alexandra; Hadlow, Narelle; Feddema, Peter; Leedman, Peter J.; O’Leary, Peter; Walsh, John P.

doi:10.1111/cen.13107

Cited by 41 publications

(32 citation statements)

References 35 publications

(48 reference statements)

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“…The results of the current study were almost similar to many others who claimed that elevation of anti-thyroid antibodies is associated with deranged TSH level (Brown et al, 2016;Loh et al, 2016;Al-Rabia, 2017). They were also compatible to two others conducted in Brazil and India which both showed the direct association between autoimmune thyroid diseases and the elevated anti-TPO (Silva et al, 2003;Unnikrishnan et al, 2013).…”

Section: Discussionsupporting

confidence: 91%

Studying the Frequency of Autoimmune Thyroid Diseases in Duhok Province

Hasan

Raziq

2019

SJUOZ

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Thyroid disorders are one of the most frequent disorders affecting endocrine system. The present study aimed to identify the frequency of thyroid disorder in our locality at Duhok city. To do so, a total of one hundred patients and one hundred apparently healthy control individuals were enrolled in this study. Samples of venous blood (5 ml) were withdrawn from patients and control subjects and analysed. Clinical assessment was performed by a specialist and each patient provided with a document supporting preliminary clinical diagnosis. Measurements of serum TSH, T3, T4, and anti-thyroperoxidase antibodies (anti-TPO antibodies) serum levels were performed. All assays were conducted at Duhok central health laboratory. Out of the one hundred patients and the one hundred control groups, forty-two and thirty candidates were randomly selected, respectively. The mean TSH serum levels of 25.87 (uIU/ml) for the patients significantly differ from that of the control group 3.55 (uIU/ml) (p<0.001). However, T3 and T4 serum levels indicated no significant difference between the two categories. Moreover, there was statisticaly significant difference (p< 0.0001) between the patients and control groups when their mean serum anti-TPO concentrations were compared. In conclusion, considerable number of subjects appeared to be candidates for deranged thyroid functions and is susceptible to autoimmune thyroid disorder.

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Section: Discussionsupporting

confidence: 91%

Studying the Frequency of Autoimmune Thyroid Diseases in Duhok Province

Hasan

Raziq

2019

SJUOZ

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“…Hence, the equilibria in individuals appropriate for their healthy state do not remain unaltered and cannot act as equivalent targets for their diseased state. Consequently, log-linearity of the TSH–FT4 relationship cannot be safely assumed over the entire functional range (27, 95–99). While linearity roughly holds true in the open loop situation and hypothyroid state, the relationship becomes progressively damped toward the euthyroid range (88, 95, 99–101).…”

Section: Interrelational Measures and Emerging New Concepts Of Thyroimentioning

confidence: 99%

“…Consequently, log-linearity of the TSH–FT4 relationship cannot be safely assumed over the entire functional range (27, 95–99). While linearity roughly holds true in the open loop situation and hypothyroid state, the relationship becomes progressively damped toward the euthyroid range (88, 95, 99–101). Within the euthyroid range, factors other than TSH dominate the expression of control (27).…”

Section: Interrelational Measures and Emerging New Concepts Of Thyroimentioning

confidence: 99%

Relational Stability in the Expression of Normality, Variation, and Control of Thyroid Function

et al. 2016

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Thyroid hormone concentrations only become sufficient to maintain a euthyroid state through appropriate stimulation by pituitary thyroid-stimulating hormone (TSH). In such a dynamic system under constant high pressure, guarding against overstimulation becomes vital. Therefore, several defensive mechanisms protect against accidental overstimulation, such as plasma protein binding, conversion of T4 into the more active T3, active transmembrane transport, counter-regulatory activities of reverse T3 and thyronamines, and negative hypothalamic–pituitary–thyroid feedback control of TSH. TSH has gained a dominant but misguided role in interpreting thyroid function testing in assuming that its exceptional sensitivity thereby translates into superior diagnostic performance. However, TSH-dependent thyroid disease classification is heavily influenced by statistical analytic techniques such as uni- or multivariate-defined normality. This demands a separation of its conjoint roles as a sensitive screening test and accurate diagnostic tool. Homeostatic equilibria (set points) in healthy subjects are less variable and do not follow a pattern of random variation, rather indicating signs of early and progressive homeostatic control across the euthyroid range. In the event of imminent thyroid failure with a reduced FT4 output per unit TSH, conversion efficiency increases in order to maintain FT3 stability. In such situations, T3 stability takes priority over set point maintenance. This suggests a concept of relational stability. These findings have important implications for both TSH reference limits and treatment targets for patients on levothyroxine. The use of archival markers is proposed to facilitate the homeostatic interpretation of all parameters.

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“…Accordingly, overt hypothyroidism is defined as serum TSH concentrations above the reference range with low free T4 (FT4) levels, while subclinical hypothyroidism is diagnosed when TSH levels are high and circulating FT4 is normal. The relationship between TSH and thyroid hormones is influenced by a number of factors, including age, smoking and thyroid peroxidase antibody status …”

Section: Introductionmentioning

confidence: 99%

Effect of l‐thyroxine administration before breakfast vs at bedtime on hypothyroidism: A meta‐analysis

Pang

et al. 2020

Clinical Endocrinology

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Hypothyroidism is resulting from a deficiency of thyroid hormones, which is common condition with potentially devastating health consequences that affect all populations worldwide. 1 Thyroid hormones are essential for growth, neuronal development, reproduction and the regulation of energy metabolism. The prevalence of hypothyroidism varies considerably across the general population, ranging between 0.2% and 5.3% in Europe, 2 0.3% and 3.7% in the USA, 3 11% in India 4 and 17.8% in China (overt hypothyroidism: 1.1%; subclinical hypothyroidism: 16.7%). 5 Longitudinal studies from large UK cohorts report an incidence rate of spontaneous hypothyroidism of 3.5-5.0 per 1000 and 0.6-1.0 per 1000 in women and men, respectively. 6The clinical presentation of hypothyroidism is nonspecific and variable. Therefore, the diagnosis of hypothyroidism is based primarily on biochemical abnormalities. The pituitary hormone thyrotropin (TSH) has a complex inverse relationship with the thyroid hormones thyroxine (T4) and triiodothyronine (T3). 7 Accordingly, overt hypothyroidism is defined as serum TSH concentrations above the reference range with low free T4 (FT4) levels, while subclinical hypothyroidism is diagnosed when TSH levels are high and circulating Abstract Purpose: To compare the effects of l-thyroxine (L-T4) administration before breakfast and administration at bedtime on hypothyroidism. Methods: The PubMed, EMBASE, Cochrane Library, Web of Science, China National Knowledge Infrastructure (CNKI) and Wanfang databases were searched to identify relevant articles. All prospective or randomized controlled studies (RCTs) comparing L-T4 administration before breakfast to the administration at bedtime in patients with hypothyroidism were included in the analysis. Results: Initially, 2884 articles were retrieved from the databases, and 10 articles were included in the quantitative analysis. The effect of L-T4 administration before breakfast compared with administration at bedtime had no statistically significant association with hormone thyrotropin (TSH) (Standardized mean differences [SMD] = 0.09, 95% confidence intervals (CI): −0.12, 0.30; P = .39), or free triiodothyronine (FT3) (SMD=−0.19, 95% CI: −0.53, 0.15; P = .28) in patients with hypothyroidism. However, the result of FT4 level was favourable for L-T4 bedtime administration group (SMD=−0.27, 95% CI: −0.52, −0.02; P = .03). Conclusion:Our meta-analysis revealed that L-T4 administration at bedtime is as effective as administration before breakfast for patients with hypothyroidism. Taking L-T4 at bedtime may be an attractive option for patients with hypothyroidism. K E Y W O R D Sadministration timing, hypothyroidism, l-thyroxine, meta-analysis How to cite this article: Pang X, Pu T, Xu L, Sun R. Effect of l-thyroxine administration before breakfast vs at bedtime on hypothyroidism: A meta-analysis. Clin Endocrinol (Oxf).

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The log TSH–free T4 relationship in a community‐based cohort is nonlinear and is influenced by age, smoking and thyroid peroxidase antibody status

Abstract: In a community-based setting, the relationship between log TSH and free T4 is complex, nonlinear and influenced by age, smoking and TPOAb status.

Cited by 41 publications

References 35 publications

Studying the Frequency of Autoimmune Thyroid Diseases in Duhok Province

Studying the Frequency of Autoimmune Thyroid Diseases in Duhok Province

Relational Stability in the Expression of Normality, Variation, and Control of Thyroid Function

Effect of l‐thyroxine administration before breakfast vs at bedtime on hypothyroidism: A meta‐analysis

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