Fig 4. Phi-adjusted cluster of random individual set points (black symbols).

The overlay depicts observed data points from euthyroid controls (n = 268, blue symbols) and LT4-treated patients (n = 207, red symbols). This simulates the possibility of a gradient change in the TSH-FT4 relationship. Reconstruction was done as described in Fig 2, but, unlike in Fig 2, the gradient phi was not fixed, rather continuously increased over the extended G_T range (1.67 to 50 nmol/s). It was randomly sampled from a normal distribution (mean 0.3, sd 0.08).