If you have had a hysterectomy for endometriosis, or you have been offered a GnRH analogue injection such as Zoladex or Prostap, there is a good chance hormone replacement therapy (HRT) has come up. And if it has, there is an equally good chance you have been left with questions. Why would you need hormones after surgery that was meant to settle things down? Why is your HRT different from a friend’s who also had a hysterectomy? Will HRT bring the pain back?

These are some of the most common questions we hear in our community, and the answers are often given in a rushed appointment, if at all. In this piece we walk through what the current guidance says, what the evidence does and does not tell us, and the questions worth taking to your next appointment.

Endometriosis is a whole-body, inflammatory condition that affects the reproductive system. It is not simply a condition of the womb, which is why removing the womb does not necessarily remove the disease. Lesions can sit on the bowel, bladder, ligaments, the lining of the pelvis and beyond, and some can remain after even very thorough surgery.

There is another important piece of the picture. Endometriosis lesions do not just respond to oestrogen circulating in the body; they can make their own. Research has shown that lesions abnormally express an enzyme called aromatase, which produces oestrogen locally. That oestrogen drives inflammatory chemicals called prostaglandins, which in turn switch on more aromatase, creating a self-sustaining loop of oestrogen and inflammation inside the lesion itself [1].

This matters for HRT because it explains why removing the ovaries does not always mean the end of symptoms, and why the type of HRT given afterwards needs careful thought. Adding oestrogen on its own, without anything to balance it, has the potential to feed any lesions that remain.

For most people who have a hysterectomy for reasons other than endometriosis, oestrogen-only HRT is standard. The progestogen part of HRT is normally there to protect the womb lining, so once the womb has gone, it is usually dropped.

Endometriosis is the exception. The European Society of Human Reproduction and Embryology (ESHRE) guideline recommends that people with a history of endometriosis who go through surgical menopause are treated with combined oestrogen and progestogen HRT, at least up to the age of natural menopause [2]. The same guideline advises against oestrogen-only treatment in menopause because of the risk of malignant transformation of endometriosis, meaning the rare possibility of remaining lesions becoming cancerous [2]. ESHRE’s 2024 guideline on premature ovarian insufficiency makes the same point: people with a history of endometriosis should have combined HRT even after hysterectomy, to avoid recurrence or malignant transformation [3].

NHS guidance reflects this. Local prescribing guidance from NHS Bristol, North Somerset and South Gloucestershire states that endometriosis is not a reason to avoid HRT, but that continuous combined HRT is advised even after total hysterectomy, until the age of natural menopause (around 51), with HRT reviewed if symptoms return [4]. Patient information from the University of Edinburgh’s reproductive health team advises continuous combined HRT for at least the first few years after removal of the ovaries, noting that a switch to oestrogen-only HRT may be discussed later, particularly for those approaching or past the age of natural menopause [5].

Tibolone, a synthetic hormone with oestrogen-like, progestogen-like and androgen-like effects, is another option some specialists use [6].

This is where real-world experience makes the guidance feel less abstract. A 2023 case report from the University of Nottingham described a 45-year-old woman who developed severe recurrent pelvic pain after five years on oestrogen-only HRT following subtotal hysterectomy and removal of both ovaries for severe endometriosis. Scans found multiple endometriomas around the cervix and a blockage of the ureter that had caused complete loss of function in one kidney [6].

In the same study, a national survey of 216 UK clinicians, including gynaecology consultants, GPs and menopause clinic nurses, found that only around two-thirds (68.6 percent) prescribed combined HRT in this situation, while 13 percent prescribed oestrogen-only HRT [6]. There was also wide variation in how long the progestogen was continued: around half prescribed it indefinitely, and others for as little as three to six months [6]. In other words, what you are offered may depend on who you see, which is exactly why it helps to know what the guidance says.

On cancer risk, a large South Korean nationwide study of 20,608 postmenopausal women with current or past endometriosis found that, apart from oestrogen-only HRT, HRT did not increase the risk of ovarian cancer; combined HRT and tibolone were not found to be risk factors [7]. It is also worth holding onto ESHRE’s strong recommendation that endometriosis itself is not associated with a significantly higher overall risk of cancer [2]. The concern with oestrogen-only HRT is about specific, rare risks, not a reason for fear of HRT altogether.

It can feel counterintuitive to take hormones after years of trying to suppress them, and some people worry so much about recurrence that they avoid HRT altogether. But losing ovarian hormones before the natural age of menopause has its own long-term costs. Loss of oestrogen at a younger age increases the risk of osteoporosis and heart disease [5], as well as bringing hot flushes, sleep disruption, vaginal dryness and changes to mood and libido.

The guidance is not “avoid HRT.” It is “use the right HRT.” For most people, the benefits of appropriately chosen HRT outweigh the risks, and that decision should be made with a clinician who understands endometriosis.

We want to be honest about the limits here. The evidence underpinning these recommendations is thin. A Cochrane review, the gold standard for summarising clinical trials, found only two small randomised trials, with 193 participants in total, looking at HRT after surgical menopause in endometriosis [8]. In one trial, 2 of 115 people on HRT had confirmed recurrence needing further surgery, compared with none of 57 people not on HRT, but the numbers were too small to draw firm conclusions [8]. The reviewers concluded that HRT could result in pain and disease recurrence, and called for more research into different HRT types [8].

The Nottingham authors also noted that the quality of evidence behind the ESHRE recommendations is limited [6]. So while combined HRT is the consensus approach, it is consensus built on clinical reasoning, case reports and small studies rather than large trials. That is a research gap our community deserves to have filled.

GnRH analogues, such as goserelin (Zoladex) and leuprorelin (Prostap), work by switching off the signals from the brain to the ovaries, creating a temporary, reversible menopause-like state. They can reduce pain and the size of lesions, and when used after surgery they can reduce the chance of symptoms coming back [9].

The downside is that low oestrogen brings menopause-type side effects, including hot flushes and, most importantly, loss of bone density. Without any added hormones, use has traditionally been limited to around six months; with appropriate “add-back” therapy, treatment can be extended to around 12 months while still remaining effective [9].

Add-back therapy means taking a small dose of hormone alongside the GnRH analogue. It might be a low dose of oestrogen with a progestogen, a progestogen alone such as norethisterone, or tibolone [10]. The doses are low enough not to undo the benefit of the injection. Research also suggests add-back should be started from the beginning rather than delayed, because waiting leads to more hot flushes and more bone loss, and that people are more likely to stay on treatment when add-back is used [11].

If you have been offered a GnRH analogue without add-back, it is reasonable to ask why, and to ask whether it would be suitable for you [10].

There are now oral options that combine hormone suppression and add-back in one place. NICE has recommended relugolix combination therapy (Ryeqo), a daily tablet containing relugolix with oestradiol and norethisterone, for adults of reproductive age whose endometriosis symptoms have already been treated medically or surgically [12]. NICE has also recommended linzagolix, taken with hormonal add-back therapy, for the same group [13].

Because Ryeqo already contains its own hormone replacement, separate HRT should not be taken alongside it [14].

If you are facing a hysterectomy, have had one, or are starting a GnRH analogue, these questions can help you get a clearer picture:

• Was any endometriosis left behind after my surgery, and how does that affect which HRT is right for me?
• Why have I been offered this particular type of HRT, and is it combined or oestrogen-only?
• How long should I stay on the progestogen part of my HRT, and when will we review it?
• If I am having a GnRH analogue, will I have add-back therapy from the start, and how will my bone health be monitored?
• What symptoms should prompt me to come back for a review?
• Can I be referred to a menopause specialist or an endometriosis specialist centre if my needs are complex?

If symptoms such as pelvic pain, bowel or bladder changes, or pain during sex return while you are on HRT, do not dismiss them. Guidance is clear that HRT should be reviewed if endometriosis symptoms come back [4].

HRT after endometriosis surgery or alongside GnRH treatment is not one-size-fits-all, and it should never be treated as an afterthought. You have every right to understand why you are being offered a particular treatment, and to ask for a plan that protects both your symptoms and your long-term health.

If this has raised questions for you, our team is here to listen, and Endometriosis UK has further information on treatment options.

1. Ferrero S, Remorgida V, Maganza C, Venturini PL, Salvatore S, Papaleo E, Candiani M, Leone Roberti Maggiore U. Aromatase and endometriosis: estrogens play a role. Annals of the New York Academy of Sciences (2014), 1317: 17-23. doi: 10.1111/nyas.12411
2. Becker CM, Bokor A, Heikinheimo O, et al.; ESHRE Endometriosis Guideline Group. ESHRE guideline: endometriosis. Human Reproduction Open (2022), 2022(2): hoac009. doi: 10.1093/hropen/hoac009
3. ESHRE, ASRM, CRE-WHiRL and IMS Guideline Group on POI; Panay N, Anderson RA, et al. Evidence-based guideline: premature ovarian insufficiency. Human Reproduction Open (2024), 2024(4): hoae065. doi: 10.1093/hropen/hoae065
4. NHS Bristol, North Somerset and South Gloucestershire ICB. Remedy: Gynaecology conditions and HRT. remedy.bnssg.icb.nhs.uk/adults/menopause/gynaecology-conditions-and-hrt
5. University of Edinburgh, Reproductive Health. Surgical menopause (patient information, 2025). reproductive-health.ed.ac.uk
6. Amer S, Bazmi S. HRT in women undergoing pelvic clearance for endometriosis: a case report and a national survey. Journal of Clinical Medicine (2023), 12(1): 336. doi: 10.3390/jcm12010336
7. Lee HJ, Lee B, Choi H, Kim T, Kim Y, Kim YB. Impact of hormone replacement therapy on risk of ovarian cancer in postmenopausal women with de novo endometriosis or a history of endometriosis. Cancers (2023), 15(6): 1708. doi: 10.3390/cancers15061708
8. Al Kadri H, Hassan S, Al-Fozan HM, Hajeer A. Hormone therapy for endometriosis and surgical menopause. Cochrane Database of Systematic Reviews (2009), Issue 1: CD005997. doi: 10.1002/14651858.CD005997.pub2
9. Surrey ES. GnRH agonists in the treatment of symptomatic endometriosis: a review. F&S Reports (2023), 4(2 Suppl): 40-45. doi: 10.1016/j.xfre.2022.11.009
10. Endometriosis.org. GnRH agonists. endometriosis.org/treatments/gnrh
11. Surrey ES. Gonadotropin-releasing hormone agonist and add-back therapy: what do the data show? Current Opinion in Obstetrics and Gynecology (2010), 22(4): 283-288. doi: 10.1097/GCO.0b013e32833b35a7
12. National Institute for Health and Care Excellence. Relugolix-estradiol-norethisterone for treating symptoms of endometriosis (TA1057), 16 April 2025. nice.org.uk/guidance/ta1057
13. National Institute for Health and Care Excellence. Linzagolix for treating symptoms of endometriosis (TA1067), 4 June 2025. nice.org.uk/guidance/ta1067
14. NHS Bath and North East Somerset, Swindon and Wiltshire. Relugolix-estradiol-norethisterone acetate (Ryeqo) for endometriosis: prescribing information (July 2025). bswtogether.org.uk