Introduction:

Thyroid function parameters in pregnant women are modified during pregnancy and are specific for each population.

Objective:

To establish reference values for thyrotropin and thyroid hormones in a population of Cuban pregnant women.

Methods:

Cross-sectional study, in the Plaza de la Revolución municipality, of 362 pregnant women without personal or family history of thyroid disease, with negative anti-thyroid antibodies and absence of lesions in the thyroid ultrasound. Maternal age, gestational age, race, smoking, number of pregnancies, use of iodine supplements, body mass index, thyrotropin, total (TT4) and free (FT4) thyroxine, total (TT3) and free (FT3) triiodothyronine were analyzed. Reference intervals were established for each parameter using the 2.5 and 97.5 percentiles as lower and upper limits, respectively.

Results:

The reference values in the first, second and third trimesters were for thyrotropin 0.1-3.3 mIUI/L, 0.6-3.4 mIU/L and 0.3-3.9 mIU/L; for TT4 90.1-204.1 nmol/L, 92.2-189.2 nmol/L and 79.8-170.4 nmol/L; for FT4 7.3-16.7 pmol/L, 6.3-17.3 pmol and 5.6-12.7 pmol/L; for TT3 1.8-3.9 nmol/L, 1.8-3.9 nmol/L and 1.7-4.0 nmol/L and for FT3 1.0-7.4 pmol/L, 0.7-6.3 pmol/L and 0.7-5.4 pmol/L, respectively.

Conclusions:

Reference values for thyrotropin and thyroid hormones were determined for the first time in a population of Cuban pregnant women. These values differ from those established by the manufacturer of the diagnostic kits and from those recommended by previous international guidelines.

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