Endocrine Abstracts

Hypothyroidism causes delayed ossification and growth retardation. T3 stimulates hypertrophic chondrocyte differentiation whereas unliganded T3 receptors (TRs) repress gene expression and maintain cell proliferation in the absence of hormone. During development the type 3 deiodinase enzyme (D3) inactivates thyroid hormones and prevents T3-access to the fetus. At birth diminishing D3 activity and increasing T3 availability triggers the onset of cell differentiation and correlat...