A raised thyroid stimulating hormone result--a 12-month follow-up study in general practice

Subclinical hypothyroidism (SCH) is common in older patients.

To review the management of patients identified with a raised thyroid stimulating hormone (TSH) result in a 12-month period and compare this to current guidelines from the New Zealand Best Practice Advocacy Centre (BPAC).

We collected laboratory data on thyroid function tests (TFTs) that were reported between December 2005 and November 2006 from two general practices with an adult population of approximately 21 000. Data were collected on symptoms, investigations, thyroid medication, family history and comorbidities. We used chi-squared tests to compare findings by age, gender and ethnicity.

Older women of European descent were more likely to be to have initial results suggesting SCH. The number of follow-up tests ranged from 0 to 5 tests in a 12-month period. Forty-eight percent of individuals did not have any follow-up investigations. Seventy-three percent of FT4 tests taken are requested concurrently with TSH. Of those who had a repeat TSH test, just over 40% had a result within the reference interval. Twenty-eight percent had two TSH results consistent with SCH. Thirty-five percent of patients with antibody results were positive. The most commonly-recorded symptoms were tiredness and weight gain.

We found inconsistencies in the management of SCH which were not related to patient characteristics such as age, gender or ethnicity. Further research is needed to determine if SCH is associated with increased morbidity and to provide a clear rationale for management of patients with SCH.