Prevalence of Undiagnosed Hypothyroidism in Europe: A Systematic Review and Meta-Analysis

Abstract

Background: Patients with undiagnosed hypothyroidism are not treated for the disease and are at high risk of developing serious complications, with major impact on public health. There is a need to systematically review the available evidence on this topic. Objective: To identify the prevalence of undiagnosed hypothyroidism in Europe. Methods: A systematic review of the literature (Medline, EMBASE, and Cochrane Central) was performed to identify epidemiological studies on the prevalence of undiagnosed hypothyroidism among European populations published between January 2008 and April 2018. The Newcastle-Ottawa Scale was used to assess the methodological quality of the included studies. Random-effects meta-analyses were performed to pool estimates of proportions (with 95% confidence intervals [CIs]) of undiagnosed (1) subclinical, (2) overt, and (3) total hypothyroidism. Results: The search returned 15,565 citations (4,526 duplicates). Twenty papers were included in the study. Fourteen and 6 studies were of good and moderate methodological quality, respectively. The results of the meta-analyses were as follows for the prevalence of undiagnosed hypothyroidism: subclinical, 4.11% (95% CI 3.05–5.31%, I² = 99.32%); overt, 0.65% (95% CI 0.38–0.99%, I² = 96.67%); and total, 4.70% (95% CI 2.98–6.79%, I² = 99.53%). According to the sensitivity analysis, the prevalence of hypothyroidism tends to be higher in female patients, in those aged ≥65 years, among studies with lower sample sizes, in those with thyroid-stimulating hormone levels <4.5 mIU/L, and in Eastern and Southern Europe. Conclusions: The current evidence suggests that a considerable proportion of the European population has hypothyroidism, particularly subclinical hypothyroidism, which is undiagnosed. This issue deserves further investigation because of possible deleterious consequences for public health.

Management of Hypothyroidism in Patients with Acute Myocardial Infarction

“…The median initial TSH level was 20 mIU/L, with higher values in the OH group (42 vs. 14 mIU/L). Patients who received treatment had a higher TSH (25 mIU/L, IQR, 13-43) when compared to those who did not receive LT4 treatment (12 mIU/L, IQR, [11][12][13][14][15][16][17][18][19], (p = 0.007). In the group of patients that were not treated with LT4, 50% were hemodynamically unstable at baseline when compared to the 21% of those who were treated.…”

“…A smaller number of studies have investigated the effect of levothyroxine (LT4) treatment and correction of hypothyroidism on clinical important outcomes, suggesting a benefit for those with overt hypothyroidism (OH) and inconsistent results for those with subclinical hypothyroidism (SCH) [8][9][10][11][12]. OH is characterized by low circulating levels of thyroxine (T4) associated with a compensatory elevation of thyroid stimulating hormone (TSH) levels [13][14][15]. SCH, which affects a larger proportion of the population (3-9%), is a biochemical diagnosis that is defined by normal levels of T4 associated with TSH levels above the upper limit of normal [1,[13][14][15].…”

“…OH is characterized by low circulating levels of thyroxine (T4) associated with a compensatory elevation of thyroid stimulating hormone (TSH) levels [13][14][15]. SCH, which affects a larger proportion of the population (3-9%), is a biochemical diagnosis that is defined by normal levels of T4 associated with TSH levels above the upper limit of normal [1,[13][14][15].…”

Thyroid disorders in subfertility and early pregnancy

“…The prevalence of hypothyroidism in pregnancy is difficult to establish as a large proportion of the disease is undiagnosed; however, is estimated at 3% with the majority being subclinical. 33 , 34 Overt hypothyroidism is estimated to have a prevalence of 0.2–1% with the greatest risk factors being iodine deficiency and autoimmune thyroiditis. 6 …”

L-T4 Therapy in the Presence of Pharmacological Interferents

“…Prevalence of undiagnosed primary hypothyroidism (PH) in Europe is 4.76% (95% CI 2.98–6.79%), precisely 4.11% (3.05–5.31%) for subclinical hypothyroidism (SCH) and 0.65% (0.38–0.99%) for overt hypothyroidism (OH) ( 1 ), paralleling the American prevalence of 4.67, 4.34, and 0.3%, respectively ( 2 ). PH prevails in females, and in those aged ≥65 years ( 1 ). Central hypothyroidism (CH) was considered 1,000-fold rarer than PH, but it may be just 20-fold rarer ( 3 ).…”