Natuurlijk verloop van subklinische hyperthyreoïdie (TEARS)

Bij subklinische hyperthyreoïdie is de TSH-waarde verlaagd en de FT4-waarde normaal. Dit komt door een licht verhoogde productie van schildklierhormoon. De T3-waarde moet bepaald worden om een T3-toxicose uit te sluiten. Andere oorzaken van een verlaagde TSH-waarde dienen uitgesloten te worden. In deze studie werd gekeken hoe vaak subklinische hyperthyreoïdie zich ontwikkelt tot hyperthyreoïdie of tot een normale schildklierfunctie.

Thyroid epidemiology, audit, and research study (TEARS): The natural history of endogenous subclinical hyperthyroidism
T Vadiveloo, PT Donnan, L Cochrane en GP Leese

For patients with subclinical hyperthyroidism (SH), the objective of the study was to define the rates of progression to frank hyperthyroidism and normal thyroid function.

Design

Record-linkage technology was used retrospectively to identify patients with SH in the general population of Tayside, Scotland, from January 1, 1993, to December 31, 2009.

Patients

All Tayside residents with at least two measurements of TSH below the reference range for at least 4 months from baseline and normal free T4/total T4 and total T3 concentrations at baseline were included as potential cases. Using a unique patient identifier, data linkage enabled a cohort of SH cases to be identified from prescription, admission, and radioactive iodine treatment records. Cases younger than 18 yr of age were also excluded from the study.

Outcome Measures

The status of patients was investigated at 2, 5, and 7 yr after diagnosis.

Results

We identified 2024 cases with SH, a prevalence of 0.63% and an incidence of 29 per 100,000 in 2008. Most SH cases without thyroid treatment remained as SH at 2 (81.8%), 5 (67.5%), and 7 yr (63.0%) after diagnosis. Few patients (0.5–0.7%) developed hyperthyroidism at 2, 5, and 7 yr. The percentage of SH cases reverting to normal increased with time: 17.2% (2 yr), 31.5% (5 yr), and 35.6% (7 yr), and this was more common in SH patients with baseline TSH between 0.1 and 0.4 mU/liter.

Conclusion

Very few SH patients develop frank hyperthyroidism, whereas a much larger proportion revert to normal, and many remain with SH.

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