Metamorphosis in amphibians is regulated by thyroxine concentration in the blood, which stimulates metamorphosis, and prolactin, which counteracts thyroxine's effect.
mˌɛɾəmˈoːɹfəsˌɪs ɪn æmfˈɪbiənz ɪz ɹˈɛɡjʊlˌeɪɾᵻd baɪ θˈaɪɹəksˌaɪn kˌɑːnsəntɹˈeɪʃən ɪnðə blˈʌd, wˌɪtʃ stˈɪmjʊlˌeɪts mˌɛɾəmˈoːɹfəsˌɪs, ænd pɹˈɑːlɐktˌɪn, wˌɪtʃ kˌaʊntɚɹˈækts θˈaɪɹəksˌaɪnz ɪfˈɛkt.