Objective: To retrospectively review health records in two general practices in Hamilton, New Zealand (NZ) linking three data sources to estimate the prevalence of diagnosed thyroid dysfunction (TD).
Methods: A record-linkage study using computerised searches to find cases of diagnosed TD by diagnostic codes, prescribing data, and laboratory data. Data was verified against computerised and written records.
Results: The prevalence of diagnosed TD was 3.1%. Overt hypothyroidism was diagnosed in 2.5%, overt hyperthyroidism in 0.2% and 'other' conditions such as goitres, nodules and thyroiditis in 0.4% of the study population.
Conclusions: This study provides a representation of TD in the community prior to mandatory iodine fortification. Our prevalence data is similar to national and international literature with the burden of TD being greater in women and in the older population.
Implications: A national study with a sufficient sample of Māori and Pacific patients is needed before supplementation with iodine is introduced.