Our data, obtained from Next Generation Sequencing (NGS) genetic screening of a large family and of a large CH cohort, in silico modelling and in vitro experiments, indicate that variations in the FOXE1 poly-Ala tract length may affect both its own transcriptional activity as well as its synergic action with PAX8 and NKX2-1 on the thyroglobulin (TG) promoter. The gene discussed is FOXE1; the disease is cyclic hematopoiesis.