Initiation of metamorphosis and control of ecdysteroid biosynthesis in insects: The interplay of absence of Juvenile hormone, PTTH, and Ca2+-homeostasis

- A high JH-titer suppresses ecdysteroidogenesis and apoptosis in PG cells.
- Upon activation of the PTTH-receptor Torso, Ca2+ enters the PG cells.
- Absence of JH can also increase [Ca2+]i in some cell types, facilitating apoptosis.
- PTTH continues to be present in adults.
- PTTH: evolutionarily ancient gonadotropin acting through steroidogenesis?