Abstract:

Introduction: Serum concentrations of the two principal biologically active thyroid hormones, thyroxine (T4) and triiodothyronine (T3) together with that of Thyroid Stimulating Hormone (TSH) are used to assess thyroid function. It is recommended that each laboratory or hospital should establish its own reference values of T4, T3 and TSH for their clients because these hormones vary with ethnicity, geographical and climatic conditions of a population. Otherwise, choosing unrelated “normal ranges” may lead to a false diagnosis. There is no documented study which has been done to determine the Thyroid hormones profile in the Ugandan general population.

Main Objective: The main objective of this study was to determine the thyroid hormones profile of students of the Faculty of Medicine, Makerere University.

Methods: A cross sectional descriptive study was done involving 72 students, with the mean age of 24.17 ± 4.48 years. Subjects who volunteered to participate in the study were interviewed; their height and body weight measured, five milliliters of blood withdrawn, and sera harvested. FT4 and T3 Radioimmuno Assay (RIA) were done and TSH was assayed using Immunoradiometric Assay (IRMA) technique. Statistical analysis was performed using SPSS. Statistically significant difference were tested by one way ANOVA and Student’s t-test, and level of significance was fixed at p < 0.05.

Results: Serum concentrations of FT4 ranged 8.897 – 27.400 pmol/L, with mean of 17.06 ± 3.847 pmol/L (95% CI of 16.112 – 17.920 pmol/L. For T3, serum concentrations ranged 0.076 – 4.490 nmol/L, with mean of 1.430 ± 0.825 nmol/L (95% CI of 1.237 -1.624 nmol/L), and serum concentration of TSH varied from 0.080 to 12.260 µlU/ml, with mean of 2.412 ± 2.284 µIU/ml (95% CI of 1.875 – 2.948 µmol/ml). Serum concentrations of FT4, T3 and TSH didn’t significantly vary with sex, age, or region of origin. Serum concentration of T3 varied with ethnicity. It was found to be lowest (0.307 ± 0.027 nmol/L) among Langi and highest (2.177 ± 0.392 nmol/L) among Gishu (p=0.016). There was no association between ethnicity and serum concentrations of FT4 and TSH. Serum concentration of TSH increased with increased BMI. It was 2.073 ± 1.907 µIU/ml for subjects with BMI of ≤ 24.9 Kg/m2, 3.588 ± 1.495 µIU/ml for subjects with BMI of 25 – 29.9 Kg/m2 and 4.450 ± 0.593 µIU/ml for subjects with BMI ≥30 Kg/m2 (p = 0.009). However, BMI had no effect on serum concentrations of FT4 and T3.

Conclusion: Serum concentrations of FT4 for students in Makerere University Faculty of Medicine ranged 8.897 – 27.440 pmol/L with the mean of 17.016 ± 3.847 pmol/L. The range is wider and the mean is higher than the values given by Institute of isotopes Company Ltd. For this population T3 ranged 0.076 – 4.490 nmol/L, with the mean of 1.430 ± 0.825 nmol/L. The mean T3 is lower and its range is wider than that given by the Institute of Isotopes Company Ltd. TSH levels ranged 0.080 – 12.260 µIU/ml, with the mean 2.412 ± 2.284 µIU/ml, and its range is wider than the one used in Mulago Hospital. This study showed that TSH concentration increases with increased BMI. It also showed lack of significant change with age, in serum concentrations of FT4, and TSH among adults aged 19 – 37 years. Furthermore, it showed that T3 levels vary with ethnicity.

Recommendations: A similar study involving a bigger sample which is more representative of Ugandans should be carried out so as to establish normal reference values of T4, T3 and TSH for Ugandans. BMI of patients should be taken into consideration during interpretation of serum TSH concentrations results.