Thyroid hormones profiling in pregnant women at various gestational periods

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Physiological changes in the endocrine environment during pregnancy result in complex alteration in indices of thyroid function, which has profound implications in the interpretation of thyroid investigations both in normal pregnancy and in the diagnosis and monitoring of gestational thyroid disease. In order to assess the thyroid function in pregnancy, serum concentration of Total thyroxine, (T4) Total triiodothyronine (T3) and Thyroid stimulating hormone (TSH) were measured in hundred pregnant women by the UMELISA Method. The hormone levels of fifty normal non-pregnant women were also measured in parallel for comparison with the pregnant group. Haemoglobin (Hb) and Packed Cell Volume (PCV) values for the pregnant women were also determined together with cholesterol levels for both groups. The results showed a significant difference in the T4 values between pregnant and non-pregnant women (p < 0.01). The mean serum Total T4 values of the pregnant women were 12.5% higher than those of the non-pregnant. T4 levels were found to increase from the 1st trimester to the 2nd and then the 3rd trimester but these values were not statistically different from each other. Mean TSH and T3 values were not significantly different for both pregnant and non-pregnant group (p > 0.05). However, the TSH value for the 1st trimester of pregnancy was significantly low, probably due to thyroidal stimulation by HCG, which shares structural homogeneity with TSH. The values of TSH and T3 obtained were all within the normal range. As expected in pregnancy, there was a significant increase in cholesterol levels as compared to the non-pregnant state (P <0.05). Thus the pregnant woman is found to be euthyroid, inspite of normal changes associated with pregnancy. To be able to come out with a precise and comprehensive interpretation of observed values obtained, there is a need to establish local reference limits taking into account the socio-economic, genetic, cultural and environmental conditions. To do this, blood from 120 donors at the blood bank at Korle-Bu Teaching Hospital, both male and female between the ages of 17 and 48 randomly chosen were collected and their thyroid hormones namely Thyroxine (T4) Trilodothyronine (T3) and Thyroid stimulating hormone (TSH) estimated using the EIA method. 95% reference limits accompanied by 90% confidence intervals were established for all three hormones using the non-parametric method. The upper limit for T4 was 154.5 nmol/l with 90% confidence of 153.9 - 160.6nml/l. The lower limit had a value of 50.1 with 90% confidence limit of 50.0 - 52.8 nmol/l. T3 was 0.45 (0.40—0.4 7) nmol/l for the lower limit and 3.36 (3.1 - 4.2)nmol/l for the upper limit. The values obtained for TSH were 0.28 (0.1 — 0.36) miu/l and 3.7 (3.3 — 4.4) miu/l for the upper and lower limits with 90% confidence. The results obtained were a bit different from those in literature but quite comparable. The TSH and T3 ranges established were narrower and lower as compared to that in literature whilst that for T4 was not so different. Variations in the ranges may be as a result of the different methods and assay reagents used and also due to genetic, social and environmental factors. Under optimal working conditions with very specific and sensitive methods, the ranges may be the same or differences may be very minimal.
This Thesis has been submitted in partial fulfilment of the requirement for the M. Sc degree in Clinical Biochemistry at the Department of Molecular Medicine, School of Medical Sciences,Kwame Nkrumah University Of Science and Technology, Kumasi, Ghana, 2000