From Formatio Reticularis:
SimThyr is a continuous simulator for pituitary-thyroid homeostasis. Pre-compiled Software is available for Mac OS X, Mac OS Classic and Windows. SimThyr was developed with Lazarus / Free Pascal (Mac OS X and Windows) or THINK Pascal (Mac OS Classic), respectively. Source code is provided for all supported platforms and may also be used in order to compile SimThyr for additional platforms.