Maternal hyperthyroidism altered the composition and gene expression of the matrix produced in vitro by chondrocytes of the offspring’s femoral epiphysis, presented as a decrease in matrix glycosaminoglycans and evidenced by a decrease in the percentage of PAS+ areas, along with reduced expression levels of Col2 and Acan and elevated Sox9 expression. The gene discussed is SOX9; the disease is hyperthyroidism.