Age- and gender-specific TSH reference intervals in people with no obvious thyroid disease in Tayside, Scotland: the Thyroid Epidemiology, Audit, and Research Study (TEARS).
OBJECTIVE
The aim of the study was to examine the association of tested TSH with age, gender, and diabetes in a large population-based cohort without evidence of thyroid disease.


METHODS
Record-linkage technology was used retrospectively to identify people without evidence of thyroid disease in the general population of Tayside, Scotland, from July 1, 2003, to December 31, 2009.


METHODS
All Tayside residents who had thyroid function tests performed were identified. Using a unique patient identifier, data linkage enabled a cohort without thyroid disease to be identified by excluding anyone with thyroid or antithyroid prescription, thyroid-related admission or surgery, treatment with radioactive iodine and/or positive thyroid antibodies. Cases below 18 years of age were also excluded.


METHODS
We measured TSH distribution among different age groups and by gender.


RESULTS
We identified the latest TSH measurements in 153127 people from the reference population after applying the exclusion criteria. There was a significant increase in median TSH (1.58 mU/L at 31-40 y to 1.86 mU/L at >90 y; P < .001) and 97.5th centile TSH (3.98 to 5.94 mU/L, respectively) with increasing age. The 2.5th centile decreased with age (0.51 to 0.31 mU/L). Patients with diabetes had marginally higher TSH concentration (1.80 vs 1.70 mU/L; P < .001).


CONCLUSIONS
The use of these age-specific reference intervals for TSH, especially in those over 70 years old, would result in the reclassification of many TSH results from "abnormal" to "normal" (within the 95th centile reference interval) and avoid unnecessary treatment.
Dundee Epidemiology and Biostatistics Unit, Division of Population Health Sciences, Medical Research Institute, MacKenzie Building, Kirsty Semple Way, University of Dundee, Dundee DD2 4BF, Scotland, United Kingdom. t.vadiveloo@dundee.ac.uk
Thenmalar
T
Vadiveloo
Peter T
PT
Donnan
Michael J
MJ
Murphy
Graham P
GP
Leese
D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D001323:Autoantibodies / Q000097:blood*; D016208:Databases, Factual / Q000706:statistics & numerical data; D003920:Diabetes Mellitus / Q000097:blood* / Q000453:epidemiology*; D005260:Female; D015292:Glycoprotein Hormones, alpha Subunit / Q000097:blood*; D006801:Humans; D008297:Male; D008485:Medical Audit / Q000706:statistics & numerical data; D008875:Middle Aged; D009017:Morbidity; D012016:Reference Values; D012189:Retrospective Studies; D012606:Scotland / Q000453:epidemiology; D016036:Seroepidemiologic Studies; D017678:Sex Distribution; D013959:Thyroid Diseases; D013961:Thyroid Gland / Q000502:physiology*; D037322:Thyrotropin, beta Subunit / Q000097:blood*
D001323:Autoantibodies; D015292:Glycoprotein Hormones, alpha Subunit; D037322:Thyrotropin, beta Subunit