Serum TSH and serum thyroid peroxidase antibody fluctuate in parallel and high urinary iodine excretion predicts subsequent thyroid failure in a 1-year study of patients with untreated subclinical hypothyroidism

Abstract

Objective: To explore the possibility of predicting decline or improvement in thyroid function over 1 year, and to investigate the correlations of serum TSH (s-TSH) with hypothyroidism-related symptoms and signs, serum thyroid peroxidase antibody (s-TPO-Ab) and urinary iodine excretion in individual patients with untreated subclinical hypothyroidism (SH). Design: Monthly repeated measurement study without intervention. Methods: Twenty-one patients without former thyroid disease who had been identified with s-TSH between 5 and 12 mU/l and normal serum thyroxine (s-T 4 ) at two occasions were enrolled. Subsequently, 13 monthly measurements of s-TSH, hypothyroidism-related symptoms and signs, serum free T 4 , s-TPO-Ab and urinary iodine excretion were performed. Results: Over the study year, s-TSH increased significantly in 5 patients, 16 had unchanged s-TSH, whereas none improved. From clinical and biochemical inclusion data, it was not possible to predict who would later increase in s-TSH. In individual patients, a highly significant correlation between s-TSH and s-TPO-Ab was found (rZ0.37, P!0.0001) and also between s-TSH and urinary iodine excretion (rZ 0.14, PZ0.034). No correlation between s-TSH and clinical symptoms and signs was observed. Time shift showed best correlation between s-TSH and s-TPO-Ab measured at the same time point, whereas urinary iodine excretion correlated best to s-TSH and s-TPO-Ab obtained 1 month later. Conclusion: At the time of inclusion, it was not possible to identify the 24% of SH patients who would show deterioration in thyroid function over the following year. Impairment in thyroid function varied in parallel with thyroid autoimmunity, whereas high urinary iodine excretion predicted high s-TSH and s-TPO-Ab 1 month later.

Variation in thyroid function in subclinical hypothyroidism: importance of clinical follow-up and therapy

“…The presence of TPO-Ab in serum is an independent risk factor for the development of HYPO in patients with SCH (16,17,46). Serum values of TPO-Ab and TSH have a parallel course in patients with SCH (43). In other words, regular measurement of TPO-Ab in addition to TSH confirms the significance of a change in TSH.…”

“…In the studies, SCH was typically defined as serum TSH above upper reference limit and with a normal serum level of an estimate of thyroxine. TPO-Ab in serum and with urinary iodine excretion as evaluated from within-person correlations (43). We studied whether the fluctuations in TSH and TPO-Ab in serum and urinary iodine excretion were in phase or not by calculating Pearson coefficients of correlations for the individual patients with time shifts between the variables.…”

Detecting True Change in the Hospital Anxiety and Depression Scale, SF-36, and Hypothyroid Score when Monitoring Patients with Subclinical Hypothyroidism

“…Participants were initially diagnosed with SCH by their family physician and subsequently included in the study if TSH was between 5 and 12 mU/L and total T4 within the laboratory reference range (60–140 nmol/L) both at first measurement and on repeated testing 3 months later, as described previously [12]. The patients were recruited from May 2004 and followed until July 2006.…”

Iodine Supplementation in Pregnancy and the Dilemma of Ambiguous Recommendations

“…However, this is a transient phenomenon as a downregulation of NIS transport of iodide into the thyroid gland will lead to escape from the Wolff-Chaikoff effect [61]. However, individuals with autoimmunity or previous thyroid disease may fail to escape from the Wolff-Chaikoff effect following exposure to high levels of iodine, and hypothyroidism may develop [62,63]. Also, hyperthyroidism may develop in susceptible individuals (e.g.…”