Fig. S1. Quantification of TSH-induced expression of thyroglobulin, BiP and PDI. Western blots as shown in Fig. 1 were scanned and densities analyzed using ImageQuant software. Results are plotted to show changes in expression over time.

Fig. S2. TSH-induced changes in protein expression. FRTL5 cells were deprived of hormones for 5 days, after which they were stimulated by the addition of 6H for the times indicated. Cells were lysed and the indicated proteins were detected by immunoblotting. To check the induction of Tg we used two independent antibodies, one raised in rabbit (DAKO) and one raised in goat (Santa Cruz), as indicated. Gels were loaded with an equal amount of protein per lane. Results show an independent experiment from the ones shown in Figs 1 and 4, to also indicate the reproducibility of the TSH-induced changes.

Fig. S3. Titrations of four antibodies used in this study. Serial dilutions of a lysate of non-activated thyrocytes were transferred to membranes and probed with the indicated antibodies (A). (B) The signal was quantified, showing that the ECL response is quantitative but hardly linear.

Fig. S4. Expression patterns of individual proteins and expression level clusters. The histograms from Figs 2B (A) and 3 (B), are shown at the same scale, to allow easy comparison between the different clusters.