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Submitted: 20 July 2016 Modified: 20 July 2016
HERDIN Record #: NCR-JAFES-16071917021210

Trimester-specific reference interval for thyroid function tests in pregnant Filipino women.

Cecilia Jimeno,
Laura Acampado,
Mary Anne Lim-Abrahan

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Background. The interpretation of thyroid hormone function during pregnancy is difficult due to its physiologic changes. Differences in iodine status in previous studies led to different intervals; therefore the use of trimester-specific, method-specific and probably country-specific reference values is advocated.

Objective. To establish trimester-specific reference interval for thyroid function tests in pregnant Filipino women.

Methodology.Six hundred sixteen pregnant patients (5-40 weeks gestation) attending a tertiary center were recruited. Level of serum thyroid stimulating hormone (TSH) was measured using immunoradiometric assay while free thyroxine (FT4), free triiodothyronine (FT3) and thyroid peroxidase antibodies (TPOAb) were measured by radioimmunoassay method.

Main outcome measures are trimester-specific reference interval based on 2.5th and 97.5th percentiles for TSH, FT4 and FT3 among TPOAb-negative pregnant patients.

Results. The reference intervals for each trimester were as follows: TSH (0.05-4.24, 0.13-3.95, and 0.20-3.00 uIU/mL); FT4 (9.80-21.88, 9.10-18.95 and 9.16-18.64 pmol/L) and FT3 (2.40-6.20, 2.77-5.00 and 2.09-3.70 pmol/L). FT4 and FT3 are strongly and negatively correlated with age of gestation (p=

Conclusions. Trimester-specific intervals among pregnant Filipino women are different from their non-pregnant counterparts and laboratory cutoffs. Thus, these reference values should be used in the country.

To establish trimester-specific reference interval for thyroid function tests in pregnant Filipino women.

Publication Type
Publication Sub Type
Journal Article, Original
Journal of the ASEAN Federation of Endocrine Societies
Publication Date
May 2016


To establish trimester-specific reference interval for thyroid function tests in pregnant Filipino women.

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