ABSTRACT
Serum total thyroxine (TT4) and triiodothyroxine (TT3) by radio-immunoassay and thyrotropin (TSH) by immunoradiomebtric assay were measured in the sera of full-term normal newborn infants of both sexes during the first 7 days of life. The results indicated that the mean (+ SE) value of TT4 (11.60 + 0.24 ug/dl) was slightly above our normal adult range while the mean of TT3 (97.48 + 2.84 ng/dl) was within the normal adult range. The levels of serum TSH in the newborns increased markedly at the first day after birth and decreased gradually after 3-7 days of postnatal life with the mean value of 5.02 + 036 nU/l. Thus the normal ranges based on the 95%confidence limits for the results of TT4 (5.00-21.00 ug/dl), TT3 (41.00-195.00 ng/dl) and TSH (0.30-18.00 mU/l) in the neonates were established in order to discriminate euthyroid infant from thyroid disorders of infancy. Serum TT3 and TSH levels of newborns during the first 3 days were found to be significantly higher than those of newborns during 4-7 days (p < 0.005). Moreover, significant sex difference was also obtained in the present study because serum TT4 and TT3 levels of the female infants were statistically higher than those of the male infants, p<0.01 and p<0.05, respectively. In addition, the concentrations of TT4 TT3 and TSH were determined and compared in these newborns following normal labour, caesarean section, gorceps and vaccuum extraction. There was a sharp increase in the mean values of serum TT4 TT3 and utilizing elective caesarean section, while a marked increase in the TSH mean was observed by the methods of forecps extraction and also caesarean section.
ABSTRACT
Serum total thyroid hormones (TT4 and TT3) have been influenced by alterations in the serum concentration of thyroxine-binding globulin (TTG), and it is necessary to determine the concentrations of free thyroid hormones (FT4 and FT3) which are the biologically active component. However, free T3 index (FT3I) or free thyroxine index (FT4I) measurements are generally accepted clinically so the usefulness and applicability of our FT3I by an in-house method euthyroids, thyroid dysfunction and patients with altered TBG were evaluated. The results indicated that the mean value of serum FT3I in 331 euthyroid subjects was 1.61 + 0.33% (+ SD) with the range of 0.90 – 2.60%. AII the FT3I values in 514 normal pregnancies and 132 chronic renal failure patients were within the normal levels which showed no overlaping results with those of 37 hypothyroids 132 hyperthyroids and 65 pregnant women with hyperthyroidism. Our FT3I gave a more precise index of thyroid status since the data correlated well with clinical observation and the usually routine test of thyroid function. The FT3I has advantages when TBG level are abnormally high or low. Total .T3 (TT3) may be elevated without an elevated TT4 in T3-toxicosis, and thus the FT3I may prevent a misdiagnosis of T3-toxicosis as demonstrated in 61 patients with T3-toxicosis. It is concluded that our FT3I would be very useful in patients with altered TBG or binding capacity and suspected T3-toxicosis.
ABSTRACT
Serum total thyroxine (TT4) measurement by radioimmunoassy (RIA) has been the most requested test of thyroid function, but high or low values may occur in euthyroid persons as a consequence of alterations in the concentrations or affinities of the serum binding proteins. The free thyroxine index (FT4I) is belive to be an ‘excellent approximation’ of the true concentration of free thyroxine (FT4), which has been shown to define thyroid status in the presence protein abnormality. Our FT4I has been developed by in-house method since 1981. Its value is derived from the ratio of TT4 to T3-uptake that corrects the TT4 for variations in thyroxine-binding proteins. The aim of this study is to compare and evaluate the values of our FT4I and of the Amerlex-M FT4 RIA kit, which is commercially available and is used as a reference method from 662 subjects divided into 5 categories; euthyroid as control, pregnant woman, chronic renal failure (CRF), hyperthyroid and hypothyroid. The results revealed that the values (+SD) of TT and T-uptake in pregnant women and in CRF are deviated from the control, but all the values of FT4I and FT4 in these subjects are within the non-pregnant euthyroid ranges. Our results also indicated that the mean values of FT4I and FT4 in euthyroid, hyperthyroid and hypothyroid differed from one another significantly (p<0.001). Moreover, significant correlations (p<0.01) of the both techniques are obtained in all categories of the subjects, utilizing Spearman’s rank correlation coefficient (rs). Therefore, our FT4I is a reliable substitute for the Amerlex FT4 assay kit in thyroid function test.