Steroids as potential modulators of thyroid hormone activity in anuran metamorphosis

Abstract

SYNOPSIS. Anuran metamorphosis is controlled by the complex interaction of several hormones. Although thyroid hormone is the major stimulatory hormone in metamorphosis and likely regulates all of the metamorphic genes directly, other hormones are involved in regulating thyroid hormone secretion and activity. Corticoids (in particular corticosterone) and the sex steroids (especially 17β estradiol) all potentially regulate thyroid hormone activity both by affecting hypothalamic and pituitary control of thyroid hormone secretion and by interacting with thyroid hormones peripherally. Although there is likely a role for endogenous corticoids in anuran metamorphosis, the role for endogenous estrogens remains to be shown. The role of these "modulators" must be fully understood, if our understanding of hormonal control of metamorphosis is to be complete.