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.
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).


METHODS
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-T4) at two occasions were enrolled. Subsequently, 13 monthly measurements of s-TSH, hypothyroidism-related symptoms and signs, serum free T4, 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 (r=0.37, P<0.0001) and also between s-TSH and urinary iodine excretion (r=0.14, P=0.034). 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.


CONCLUSIONS
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.
Karmisholt
Jesper
J
Department of Endocrinology and Medicine, Aalborg Hospital, Aarhus University Hospital, 9000 Aalborg, Denmark. jsk@rn.dk <jsk@rn.dk>
Laurberg
Peter
P
D000328:Adult; D000368:Aged; D001323:Autoantibodies / Q000097:blood*; D015551:Autoimmunity; D015415:Biomarkers / Q000097:blood / Q000652:urine; D005260:Female; D006801:Humans; D007037:Hypothyroidism / Q000097:blood* / Q000201:enzymology / Q000276:immunology / Q000652:urine*; D007453:Iodide Peroxidase / Q000276:immunology*; D007455:Iodine / Q000652:urine*; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D012720:Severity of Illness Index; D013960:Thyroid Function Tests; D013963:Thyroid Hormones / Q000097:blood; D013972:Thyrotropin / Q000097:blood*
D001323:Autoantibodies; D015415:Biomarkers; D013963:Thyroid Hormones; D013972:Thyrotropin; D007455:Iodine; D007453:Iodide Peroxidase