EVERYDAY SCIENCE

Detailed explanation-1: -Thyroid hormone (TH) is the most important hormone in frog metamorphosis, a developmental process which will not occur in the absence of TH but can be induced precociously by exogenous TH.

Detailed explanation-2: -The function of thyroxine hormone in frogs is to control the metamorphosis of the frog. Metamorphosis is a biological process where some animals and insects undergo extreme physical changes.

Detailed explanation-3: -The lower concentration of thyroxine only induces the tadpole to a certain point of metamorphosis in spite of treatment continued for more than one month. In such a stable tadpole the metamorphosis progresses only when the concentraion is raised.

Detailed explanation-4: -The process of metamorphosis is controlled by hormones such as thyroxine. This hormone is produced by the thyroid gland and its synthesis requires the presence of iodine. Thus, iodine is essential for metamorphosis because it is required for the synthesis of thyroxine hormone.

Detailed explanation-5: -During metamorphosis, negative regulation of thyrotropin by thyroxine (T4) is relaxed allowing higher whole-body levels of T4 that enable specific responses at the tissue/cellular level. Higher local thyroid cellular signaling leads to cell-specific responses that bring about localized developmental events.