Factors Influencing Clinical Decisions to Initiate Thyroxine Therapy for Patients With Mildly Increased Serum Thyrotropin (5.1-10.0 mIU/L)

Fatourechi, Vahab; Lankarani, Mahnaz; Schryver, Patricia G.; Vanness, David J.; Long, Kirsten Hall; Klee, George G.

doi:10.4065/78.5.554

Cited by 20 publications

(12 citation statements)

References 15 publications

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“…For subclinical hypothyroidism with a mild TSH concentration elevation, there is no consensus on the benefit of treatment (1,22,23,24), and mild TSH concentration elevation may frequently be due to causes other than (19,20), age-related physiological changes in pituitary-thyroid axis function (25,26), or simply being in the upper tail of the physiological distribution of TSH concentrations. In a study carried out in the Mayo Clinic in 1995-1996, levothyroxine was prescribed for only 20% of people with serum TSH concentrations of 5-10 mU/l without evidence of autoimmune thyroiditis (27). The declining prevalence of mild TSH concentration elevation without TPO antibodies that we observed may suggest that people with a mild TSH concentration elevation without evidence of autoimmune thyroiditis are increasingly being treated with levothyroxine.…”

Section: Huntmentioning

confidence: 71%

Changes in the prevalence of hypothyroidism: the HUNT Study in Norway

Åsvold

Vatten

Bjøro

2013

European Journal of Endocrinology

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Objective: Untreated hypothyroidism is common in iodine-replete areas. Frequent thyroid function testing and use of levothyroxine treatment for subclinical hypothyroidism suggest that the prevalence may have decreased. Therefore, in this study, we examined changes in the prevalence of hypothyroidism in a Norwegian county from 1995-1997 to 2006-2008 The corresponding decrease among men was 43% from 0.21 to 0.12% (PR 0.57; 95% CI 0.28-1.16). The prevalence of untreated subclinical hypothyroidism decreased by 64% from 3.0 to 1.1% in women (PR 0.36; 95% CI 0.31-0.42) and decreased by 54% from 2.1 to 1.0% in men (PR 0.46; 95% CI 0.38-0.56). Conversely, the prevalence of treated hypothyroidism among women increased by 60% from 5.0 to 8.0% (PR 1.60, 95% CI 1.50-1.71), and the corresponding prevalence in men doubled from 1.0 to 2.0% (PR 1.96; 95% CI 1.59-2.41). The prevalence of any form of hypothyroidism remained essentially similar at 9% in women and 3% in men. Conclusions: The prevalence of untreated hypothyroidism in this Norwegian county decreased strongly from 1995-1997 to 2006-2008. The findings suggest that the prevalence of untreated hypothyroidism in populations with easy access to thyroid function testing and levothyroxine treatment may now be low.

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Section: Huntmentioning

confidence: 71%

Changes in the prevalence of hypothyroidism: the HUNT Study in Norway

Åsvold

Vatten

Bjøro

2013

European Journal of Endocrinology

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“…The finding of no significantly increased risk of CHD among the high proportions of adults with minimal TSH elevations is important because many patients with minimal TSH elevations are treated in clinical practice (17). The threshold TSH to define and treat subclinical hypothyroidism remains controversial (2,3,18).…”

mentioning

confidence: 99%

Subclinical Hypothyroidism and Cardiovascular Risk: How to End the Controversy

Rodondi

Bauer

2013

The Journal of Clinical Endocrinology &Amp; Metabolism

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T he indications for screening and TSH threshold levels for treatment of subclinical hypothyroidism have remained a clinical controversy for over 20 years. Subclinical thyroid dysfunction is a common finding in the growing population of older adults, occurring in 10 -15% among those age 65 and older, and may contribute to multiple common problems of older age, including cardiovascular disease, muscular impairment, mood problems, and cognitive dysfunction (1). In 2004, both the U.S. Preventive Services Task Force (2) and a clinical consensus group of experts (3) concluded that the existing evidence about the association between subclinical hypothyroidism and cardiovascular risks, primarily cross-sectional or case-control studies (4), was insufficient. For example, a frequently cited analysis from the Rotterdam study found a cross-sectional association between subclinical hypothyroidism and atherosclerosis, as measured by abdominal aortic calcification (odds ratio, 1.7; 95% confidence interval [CI], 1.1-2.6) and prevalent myocardial infarction (MI) (odds ratio, 2.3; 95% CI, 1.3-4.0) (5). Conversely, the prospective part of this study included only 16 incident MIs; the hazard ratio (HR) for subclinical hypothyroidism was 2.50, with broad 95% CIs (0.70 -9.10). Potential mechanisms for the associations with cardiovascular diseases among adults with subclinical hypothyroidism include elevated cholesterol levels, inflammatory markers, raised homocysteine, increased oxidative stress, insulin resistance, increased systemic vascular resistance, arterial stiffness, altered endothelial function, and activation of thrombosis and hypercoagulability that have all been reported to be associated with subclinical hypothyroidism (1, 6).Since 2004, several large prospective cohorts investigated this issue, leading to conflicting data on the associations between subclinical hypothyroidism and cardiovascular risk (7-9). Study-level meta-analyses tried to clarify these conflicting data (9, 10), and found modestly increased risks for coronary heart disease (CHD) and CHD mortality, but with heterogeneity among individual studies that used different TSH cutoffs, different confounding factors for adjustment, and varying CHD definitions (9). To help clarify this issue, we formed the Thyroid Studies Collaboration, which successfully collected individual participant data from 55 287 participants with 542 494 person-years of follow-up from 11 international prospective cohorts. In a series of individual participant data analyses, generally considered the highest level of nonrandomized evidence (11), we found that subclinical hypothyroidism was associated with an increased risk of CHD events and CHD mortality in adults with higher TSH levels (12) and with an increased risk of heart failure events (13), particularly when TSH exceeds 10 mU/L.A particular shortcoming of the available evidence to date is the lack of randomized clinical trials on relevant clinical outcomes (2, 3). Small, short-term trials among individuals with subclinical hypothyroi...

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“…In my experience, the usual required daily levothyroxine dose is 50 to 75 µg. 51 Anticipating future progression of thyroid failure, some endocrinologists recommend a full replacement dose. I prefer to start with a daily dose of 25 to 75 µg, depending on the age of the patient, the level of free thyroxine, and the serum TSH level.…”

Section: Levothyroxine Therapy For Schmentioning

confidence: 99%

Subclinical Hypothyroidism: An Update for Primary Care Physicians

Fatourechi

2009

Mayo Clinic Proceedings

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295

186

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Subclinical hypothyroidism (SCH), also called mild thyroid failure, is diagnosed when peripheral thyroid hormone levels are within normal reference laboratory range but serum thyroid-stimulating hormone (TSH) levels are mildly elevated. This condition occurs in 3% to 8% of the general population. It is more common in women than men, and its prevalence increases with age. Of patients with SCH, 80% have a serum TSH of less than 10 mIU/L. The most important implication of SCH is high likelihood of progression to clinical hypothyroidism. The possibility that it is a cardiovascular risk factor has been a subject of debate. Large-scale randomized studies are needed for evidence-based recommendations regarding screening for mild thyroid failure and levothyroxine therapy for this condition. Currently, the practical approach is routine levothyroxine therapy for persons with a persistent serum TSH of more than 10.0 mIU/L and individualized therapy for those with a TSH of less than 10.0 mIU/L. © 2009 Mayo Foundation for Medical Education and ResearchOn completion of this article you should be able to: (1) S ubclinical hypothyroidism (SCH) is defined as a serum thyroid-stimulating hormone (TSH) level above the upper limit of normal despite normal levels of serum free thyroxine. 1 Serum TSH has a log-linear relationship with circulating thyroid hormone levels (a 2-fold change in free thyroxine will produce a 100-fold change in TSH). Thus, serum TSH measurement is the necessary test for diagnosis of mild thyroid failure when the peripheral thyroid hormone levels are within normal laboratory range. 1 The individual range for peripheral thyroid hormones is narrower than the population reference laboratory range; therefore, a slight reduction within the normal range will result in elevation of serum TSH above the normal range.Subclinical hypothyroidism or mild thyroid failure is a common problem, with a prevalence of 3% to 8% in the population without known thyroid disease. 2,3 The prevalence increases with age and is higher in women. 2 After the sixth decade of life, the prevalence in men approaches that of women, with a combined prevalence of 10%. 2 Antithyroid antibodies can be detected in 80% of patients with SCH, and 80% of patients with SCH have a serum TSH of less than 10 mIU/L.Before diagnosis of SCH, other causes of an elevated TSH level, such as recovery from nonthyroidal illness, assay variability, presence of heterophile antibodies interfering with the TSH assay, and certain cases of central hypothyroidism with biologically inactive TSH and thyroid hormone resistance, should be excluded. However, the most common cause of elevated TSH is autoimmune thyroid disease. 1 Previous radioiodine therapy, thyroid surgery, and external radiation therapy can also result in mild thyroid failure. Transient SCH may occur after episodes of postpartum, silent, and granulomatous thyroiditis. 1,4 The clinical importance of and therapy for mild elevation of serum TSH (<10 mIU/L) 5 and the exact upper limit of normal for the serum TSH ...

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Factors Influencing Clinical Decisions to Initiate Thyroxine Therapy for Patients With Mildly Increased Serum Thyrotropin (5.1-10.0 mIU/L)

Cited by 20 publications

References 15 publications

Changes in the prevalence of hypothyroidism: the HUNT Study in Norway

Changes in the prevalence of hypothyroidism: the HUNT Study in Norway

Subclinical Hypothyroidism and Cardiovascular Risk: How to End the Controversy

Subclinical Hypothyroidism: An Update for Primary Care Physicians

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