Thyroid SPOT

Thyroid SPOT is a medical application developed for the Singapore Institute for Clinical Sciences for the treatment of patients with a thyroid imbalance.

The production of thyroid hormone FT4 is controlled by the hypothalamus and the pituitary gland by way of a feedback system by excreting the thyroid stimulating hormone TSH in response to the level of FT4. The relation between the TSH and FT4 was found to be (by S.L. Goede):

TSH = S/exp(φ FT4)

When treating patients with a thyroid imbalance, the optimum setpoint for the feedback loop is given by:

[FT4] = ln(φ S √2)/φ, [TSH] = 1/(φ √2)

where the parameters S and φ are obtained by fitting the model to measured FT4-TSH combinations obtained during treatment.

Formulated like this, the numerical condition of the optimization problem is far from ideal. The sensitivity of the objective function with respect to the parameters varies widely, and the parameters have a huge range.

The model can be reformulated by choosing for the model parameters the setpoint-coordinates themselves. An additional advantage of this approach is that the calculated parameter precision applies directly to the extracted setpoint.

The Windows version of ParXCL was then packaged in a Windows UI designed by Raymond Verbruggen from Focussing BV. The UI controls ParXCL directly by using its scripting interface, and JSON for data transport.