Ruhr-Universitšt Bochum

SimThyr, a simulator of thyrotropic feedback control, here on Windows XP, supports a wide range of hardware and operating systems.

SimThyr, a simulator of thyrotropic feedback control, here on Mac OS X 10.6 (Snow Leopard) supports a wide range of hardware and operating systems.

Thyroid hormones play an essential role for metabolism, growth and differentiation. Therefore, exact regulation of thyroid hormone levels is vital for most organisms. Although the principles of thyrotropic feedback control have been described decades ago we still have not yet gained a comprehensive understanding of its dynamics.

Recently, significant progress has been made with mathematical modelling of thyroid homeostasis. However, due to nonlinear interactions, these cybernetic modells cannot simultaneously describe static and dynamic behaviour. This gap may be filled with computer simulations that additionally provide a more intuitive insight into the dynamics of thyrotropic feedback.

SimThyr is an interactive simulation program of pituitary thyroid feedback control that enables one to study the relationship between structure and behaviour of thyroid homeostasis, i.e. between the architecture of the intercausal network and the resulting hormone levels. Its goal is to support both science and education in thyroidology.

SimThyr is based on a parametrically isomorphic model of the overall system. Applications of this program cover research, including development of hypotheses, and education of students in biology and medicine, nurses and patients.

SimThyr has significantly contributed to research on thyroid homeostasis. It helped to prove a new hypothesis about the emergence of pulsatile TSH release and it delivered key indications that central hyperdeiodination leads to low T3 syndrome in humans. Additionally, it suggested the existence of epigenetic effects of thyroid status on central homeostasis. Other research projects used SimThyr to investigate the effects of certain structure parameters of the feedback loop on diagnostic quality in the evaluation of thyroid function. Furthermore, the software is used for educational projects at several locations.

The algorithms underlying the continuous simulation process have been released in several publications. They may also be applied in form of classical mathematical modelling. However, using them in a computer simulation provides a deeper and more intuitive insight into temporal dynamics of thyroid homeostasis.

Over the previous years, SimThyr has received several certificates and awards.

This is a free and open source application that is offered on the base of a BSD licence. Binaries are available for Mac OS, Mac OS X and Windows, source code requires THINK Pascal (for Mac OS Classic) or Lazarus/Free Pascal (for Mac OS X, Windows and Linux).

SimThyr on Windows XP
SimThyr on Mac OS X 10.4 (Tiger)
SimThyr on Mac OS X 10.5 (Leopard)

SimThyr project entry at