Hormone implants in hormone replacement therapy (HRT)
Hormone Implants
Hormone implants are small crystalline slow-release pellets containing 100% body / bio-identical hormones. Implants are indicated where all other HRT options have been found to be ineffective.
Both estradiol 50mg and testosterone 100mg implants are unlicensed for use in the UK but can be used by specialists.
Implants are usually inserted every 6-8 months, but not more frequently. A blood test is required every 6 months to monitor the hormone levels with the dose and frequency adjusted accordingly. Our guidelines follow evidence based safe practice to ensure therapeutic hormone levels are maintained. The physiological estradiol range is 250-600pmol but exceptionally a higher limit may be agreed. The implant cannot be replenished without a current up-to-date result.
The decision to use implants is based upon individual needed. There is no specific age cut off when implants are discontinued but assessed on individual risks and benefits.
Implant procedure
Implants are inserted under the skin, usually in the abdomen (stomach) or in the buttock. Following a local anaesthetic, a small 5-10mm cut is made in the skin. Using an ‘introducer’ the implant is inserted into the subcutaneous (fat) layer of the skin. The wound is closed with steristrips or a dissolvable suture (stitch) and a sterile dressing which should remain in place for 48 hours. The stitch will dissolve and fall out in 7-10 days or may be removed by your GP or practice nurse.
| Common complications |
You may experience localised bruising, mild pain and discomfort at the wound site for a few days after the procedure. Simple painkillers will help reduce symptoms e.g: paracetamol or ibuprofen. You will be left with a small scar from the incision. |
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Rare complications |
The wound may become infected. If the wound appears inflamed (red), hot with a discharge (pus) then an antibiotic may be prescribed by your GP. Implants may be rejected. The implant cannot be replaced until your next appointment but top-up transdermal HRT can be used in the interim. |
Risks and benefits of estradiol implants
Please speak to your clinician for individualised risks and benefits and ensure you are happy to continue this treatment. The risks and benefits of implants are the same as for any transdermal (via the skin) hormone replacement therapy (HRT).
Benefits include improved response when other treatments have failed including long-term bone protection. With the serum estradiol levels maintained within normal physiological parameters the risks include thromboembolic risk (blood clots) or stroke, but comparable to other transdermal HRT estrogen.
Tachyphylaxis
Specific to implants, the estradiol levels can accumulate in the blood over time. Studies have found that the estradiol may reach higher than normal levels with about 3% cases symptoms return sooner than six months. This is known as tachyphylaxis. To prevent this risk, if your estradiol results are supraphysiological (high) the next implant dose may be reduced or deferred.
Testosterone implants
Testosterone was licensed as a patch for loss of libido but was withdrawn for commercial reasons, not safety concerns. The current unlicensed testosterone implant delivers a female equivalent dose and has a low risk of side effects. The most common side effects are excess facial or body hair growth which is generally reversible upon discontinuation. Less commonly acne, male pattern hair loss or deepening of the voice may occur.
Blood tests
To reduce the risks of tachyphylaxis a blood test is required two weeks before every implant. If the result is too high your implant may be deferred until it has returned within range. Some menopause symptoms may return before the next implant is due, in which case a top-up of estradiol patch or gel can be prescribed by your GP. You must stop using top-up estradiol or testosterone seven days before the blood test but may be resumed straight afterwards.
Endometrial protection of the womb
If you have a uterus (womb) you will also be prescribed a progestogen/progesterone. This is to prevent the risk of developing endometrial hyperplasia (thickening of the womb lining) which may lead to endometrial cancer. Without adequate progestogenic opposition the additional risk increased cancer risk is 5 cases per 1000 after 5 years of use. The gold standard protection with implants is the Mirena Levonorgestrel intrauterine device (IUS) but other options can be discussed with your specialist.
Discontinuing estradiol implants
Estradiol implants should be considered as a non-reversible HRT and cannot be removed once inserted. Implants are not suitable if you plan to become pregnant within the next 12 months.
Estradiol implants give a therapeutic effect for 6-8 months. However, the residual implant may continue to release small amounts of estradiol for up to 18-24 months. If you have a uterus (womb) a progestogen must continue until the serum estradiol blood test is within the postmenopausal range (<100pmol).