Modeling the dynamics of thyroid hormones and related disorders

Abstract

In this study, a dynamic simulation model for thyroid hormone system is constructed. The objective of this work is to first generate the dynamics of the hormones involved in thyroid hormone system in healthy body, and then to adapt the model to portray the dynamics of certain common thyroid disorders. The ultimate aim is to provide a platform for scenario analysis to support medical education, training and research, without risking patients’ health. Initially, the model structure is tested by standard structure validity tests. After the validation part, four common thyroid disorders are simulated. Firstly, Graves’ disease, the most common source of hyperthyroidism, is addressed. Goiter formation, effect of iodine availability on the severity of the disease, and increased T3/T4 –a commonly used diagnostic measure in hyperthyroidism– are all well captured by the model. Other typical behaviour of hormones and glands are also well mimicked by simulations. Secondly, iodine deficiency, one prevailing cause of hypothyroidism, is discussed for two different levels of daily iodine intake. The model was able to depict all the characteristic changes including the goiter formation and increase in T3/T4 in these two scenarios, both independently and comparatively. Thirdly, the transient inhibitory effect of excessive iodine intake on thyroid gland is discussed. The model is able to demonstrate the enlargement in thyroid volume and the mild decline in thyroid hormones. Lastly, a condition called subacute thyroiditis, a common disorder in which thyroid gland is exposed to inflammation, is analysed. The typical triphasic clinical course of subacute thyroiditis, comprised of thyrotoxicosis, hypothyroidism and normal thyroid functioning is well represented by the model. In conclusion, with respect to both qualitative and quantitative information in literature, and interviews with the medical doctors, the model exhibits an acceptable degree of validity and is able to cover a wide range of thyroidrelated disorders.