Progestins are synthetic progesterone-like hormones. They may also be referred to as progestagens - a term that encompasses both naturally occurring progesterone and synthetic forms. It is not known exactly how progestins relieve the symptoms of endometriosis, but it is believed that they suppress the growth of the endometrial implants in some way, causing them to shrink gradually and eventually disappear. Up to 80 per cent of women have relief of pain caused by endometriosis with progestins²⁰.

Possible side effects

Progestins come in a variety of forms, each with its own advantages and disadvantages. Like all hormonal treatments, there are potential side effects with progestin; however women usually experience fewer side effects with this treatment. There are oral forms which are taken daily, or long-acting forms given through injection, implant or IUD.

Side effects may include:

• Irregular bleeding
• Breast tenderness
• Acne
• Abdominal bloating
• Fluid retention
• Mood changes / depression
• Nausea / vomiting
• Dizziness
• Tiredness
• Weight gain

Content updated 30 November 2011