Thyrotrophin and free thyroxine trimester-specific reference intervals in a mixed ethnic pregnant population in the United Arab Emirates.
BACKGROUND
Physiological alterations in the homeostatic control of thyroid hormones cause changes in thyroid function tests in pregnant women. A lack of method, trimester and population-specific reference intervals for free thyroxine (FT4) and thyrotrophin (TSH) makes interpretation of FT4 and TSH levels in pregnancy difficult. We established trimester-specific reference intervals for TSH and FT4 in a mixed ethnic population of pregnant women attending two antenatal clinics in the United Arab Emirates.


METHODS
TSH and FT4 result from 1140 women with uncomplicated singleton pregnancy were available. The 95% reference intervals were determined for TSH and FT4 for each trimester for Arab women from the United Arab Emirates and other Arab countries and Asian women.


RESULTS
Suppressed TSH levels in the first trimester recovered to non-pregnant levels in the third trimester. There was a significant difference in TSH levels between trimesters 1 and 2, and 2 and 3 (p<0.0005). There was no significant difference in the TSH levels between the various ethnic groups. Mean FT4 levels decreased with each progressive trimester in all groups. There were significant differences in FT4 levels between all three trimesters (p<0.005), especially between the first and second trimesters. FT4 differed significantly between UAE nationals and Asians in the first and second trimesters (p<0.005).


CONCLUSIONS
In general, the findings were in keeping with earlier reports. Use of trimester-specific reference intervals should help in the appropriate interpretation of thyroid hormone results in the mixed UAE population.
Department of Laboratory Medicine, Tawam Hospital, Al Ain, UAE. gurdeep1@emirates.net.ae
Gurdeep Singh
GS
Dhatt
Ravichandra
R
Jayasundaram
Laila Abdul
LA
Wareth
Nico
N
Nagelkerke
Krishnasamy
K
Jayasundaram
Etidal Ali
EA
Darwish
Anselma
A
Lewis
D000293:Adolescent; D000328:Adult; D005006:Ethnicity; D005260:Female; D006801:Humans; D008875:Middle Aged; D011247:Pregnancy; D011264:Pregnancy Trimesters / Q000097:blood* / Q000208:ethnology; D012016:Reference Values; D013972:Thyrotropin / Q000097:blood*; D013974:Thyroxine / Q000097:blood*; D014479:United Arab Emirates / Q000208:ethnology
D013972:Thyrotropin; D013974:Thyroxine