There are also nervous system changes and behavioral changes associated with the transition to the adult form.
Active ingredient is thyroxine or tri-iodothyronine.
Molecular control is incompletely understood. Early in the process, messenger RNAs for thryoxine receptors are synthesized at higher rates due to the increase in thyroid hormone. The early part of metamorphosis is thus characterized by autoinduction. Coordination of events, i.e., assuring that events occurring in different parts of the body are correctly timed, seems to come about as a result of differences in the threshold concentration for thryoxine. In other words, tissues show differential competence to respond to the hormone.