Hyperthyroidism and pregnancy. I. Serum TBG level in normal pregnancy

Methods for preparation and qualitative evaluation of the reagents necessary for direct radioimmunoassay of thyroxin-binding globulin (TBG) in serum are described. The reagents are: purified TBG necessary as antigen in preparing the labelled product and plotting the reference curve; 125I-TBG; anti-TBG rabbit serum. The technical stages characteristic of the RIA system are presented. TBG level determined in normal volunteers (about 80% males and 20% females, young subjects living in Bucharest area) was found to be 15.6 +/- 2.23 mg L-1 (M +/- SD) and the PBI, T4, and T3 values at the onset were normal. In another lot formed only from women TBG was 17.3 +/- 3.50. Assay of 136 pregnant women between the 2nd an 9th month of pregnancy showed values of 22.46 (2nd month) and 32.23 mg L-1(8th month). The shape of the increase curve during pregnancy shows two main stages. The importance of the serum TBG level as an additional criterion in the diagnosis of pregnancy (even in the first weeks of life of the foetus) and as an indicator of the placentar function is discussed.