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अमूर्त

New Immunoassays of Bioactive TSH Improve Detection of Thyroid Disorders

Sandrine Donadio-Andrei and Catherine Ronin

Background: TSH assays have long been showing discordances, especially in the upper limit of the reference range. There is thus a need to improve TSH measurement and detection of thyroid dysfunction. This study aimed at evaluating the ability of new TSH assays to detect early thyroid deficiency in a healthy population with no suspicion of thyroid disorders.

Methods: We selected 797 subjects without declared hyperthyroidism, hypothyroidism, goiter, personal or familial thyroid dysfunction, thyroid autoimmunity or medication among 1,623 individuals recruited in a multicenter prospective study (2012-2014). Hypothyroidism-related clinical signs (hCS) were collected, TSH and thyroid hormones levels measured by routine tests and 4 new assays based on calibration with a biologically active recombinant TSH. Analysis was performed as a function of gender and age (<60 y and ≥ 60 y).

Results: Expression of hCS appeared to vary as a function of gender and age in healthy individuals. The cohort displayed a higher percentage of males with no hCS in both <60 y (45.9%) and ≥ 60 y (33.9%) but a high percentage of females with at least 3 hCS in both <60y (29.7%) and ≥ 60y age groups (39.7%). FT3 and FT4 levels were different in males and females <60 y (p<0.05 and p<0.01 respectively) in contrast to TSH values. When we analyzed the population with elevated TSH (>97.5th centile), FT4 levels were found to be slightly reduced and the expression of hCS increased (median, 2.0 vs. 1.0) when TSH was measured by the new assays compared to the routine assay. Detection of subclinical TSH was particularly improved in elderly women.

Conclusion: New assays measuring bioactive TSH exhibited a good correlation with expression of hCS and FT4 levels, especially in ≥ 60 y women. Such assays may improve the monitoring of elderly people as well as the whole healthy population, especially in the context of environmental hazards.