Session: SUN 414-431-HPT Axis Biology
Poster Board SUN-416
Aim: To report TSH secretion data of a large number (n=117) healthy subjects , who underwent 10-min blood sampling during 24-h.
Methods: TSH was measured by a sensitive IFMA (Wallac Oy, Turku, Finland), and calibrated against WHO IRP 80/558. Secretion parameters were calculated with an automatic Matlab-based deconvolution program (4).
Results: The age range was 22-77 yr, BMI 18-39 kg/m2, FT4 9.4-23.1 pmol/l, number of pulses 18.4 ± 4.3 /24-h (mean ± SD), basal secretion 20.7 ± 11.4 mU/l, pulsatile secretion 19.4 ± 12.2 mU/l and total secretion 40.1 ± 21.1 mU/l. There were no sex differences in pulse frequency, hormone half-lives, secretion modes, basal, pulsatile and total secretion or pulse regularity. Basal and total TSH secretion were linearly dependent on BMI with higher basal and total TSH secretion with higher BMI (β basal 0.63 ± 0.20, P=0.003, β total secretion 0.807 ±0.39, P=0.039). Age and gender were not significant factors in the full regression model. Body mass index did not correlate with other secretion parameters, including pulse frequency, half-lives, secretion mode (time needed for reaching the maximal secretion rate within a pulse), mean pulse mass and pulse regularity. Free T4 levels did not correlate with any of the TSH deconvolution parameters, including pulse frequency hormone half-lives , basal or total secretion, BMI and age.
Conclusion: TSH secretion appears to be robust across sex and age, and only weakly dependent on BMI. This result contrasts sharply with secretion parameters derived from deconvolution of 24-h plasma profiles of GH, ACTH and prolactin in comparable healthy controls series, which all are dependent on BMI, age and gender, albeit in different ways.
Nothing to Disclose: FR, PK, HP, NRB, AMP, JDV
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