Functions of progesterone are many, for instance:

• Precursor of oestrogen and testosterone
• Maintain secretory endometrium
• Protects against breast fibrocysts
• Natural diuretic
• Natural anti-depressant
• Helps maintain thyroid hormone action
• Precursor of cortisone synthesis by adrenal cortex

Progesterone can also be converted to other important hormones, which are essential for blood pressure, stress response and sugar and electrolyte balance.