The evolution of thyroid hormones in pregnancy. An analysis of 125 cases in the Yaounde general hospital

This study was aimed at determining the evolution and the kinetics of thyroid hormones in a sub-population of pregnant women in Cameroon. We carried out a prospective study (from January 2005 to January 2006) on 125 consenting pregnant women at the Yaounde General Hospital. Clinical and gyneco-obstetric data with the gestational age were noted on a pre-designed questionnaire. Blood samples were drawn for serum assay of thyroxine (T4), triiodothyronine (T3) and thyroid stimulating hormone. The results were read with the 'Oakfield health care' Gamma ' 12 counter using the RIASTAT software. These patients, divided into four groups consisted of: 32 non pregnant women in the control group; 33 pregnant women in the first trimester; 30 pregnant women in the second trimester and 30 at the third trimester. The mean serum levels of T3 and T4 were relatively high in all pregnant women (irrespective of the gestational age) than in the control group. Serum levels of T3 and T4 were raised the first trimester with and progressively reduced in 2. and 3. trimester. On other hand, TSH levels progressively increased as from the 2. trimester to attain a maximum in the 3. trimester. We can therefore conclude that blood levels of thyroid hormone as well as TSH vary during pregnancy and differ in titres with respect to the gestation age. (authors)