Endocrine Abstracts

Similar to thyroid hormones, the calcineurin/NFAT pathway regulates bone mass via its actions in osteoblasts and by indirect effects on osteoclast function. Calcineurin is a calcium- and calmodulin-activated phosphatase that dephosphorylates the transcription factor NFAT enabling its translocation to the nucleus. RCAN2 is an inhibitor of calcineurin that is stimulated by T3 in brain, heart and skeletal muscle although its expression in bone has not been studied. Thu...

The prohormone T4 represents the majority of circulating thyroid hormones, whereas 80% of the active hormone T3 is derived from T4 by the actions of the type 1 and type 2 deiodinase enzymes (D1 and D2). Local generation of T3 by D2 regulates ligand supply to the nuclear T3-receptor in pituitary, brown adipose tissue and brain, and this enzyme is also expressed in bone. Hypothyroidism in children causes delayed bone age and growth retardation, whereas thyrotoxicosis in adults c...