Endocrine Abstracts

Oestrogen implants are one method of delivering hormone replacement therapy to post-menopausal women. The use of such implants has been associated with the phenomenon of tachyphylaxis, where menopausal symptoms return before the next implant is due, even in the presence of normal or high serum oestrodiol levels. It has been suggested that intervals as long as one year should be left between implants and that trough oestrogen levels should be measured prior to implantation.

A 46-year-old woman presented with hot sweats. Her serum oestrodiol level was markedly elevated at 1755 pmol/l (post menopausal range 117–268 pmol/l) and serum gonadotrophins undetectable (FSH <0.3 U/l). Following a hysterectomy and left salpingo-oopherectomy in 1993, she had her right ovary removed for a right hydrosalpinx in 1998. Subsequently, she received multiple oestrogen implants to control menopausal vasomotor symptoms. Over a period of six and a half years, she received 100 mg oestrodiol implants approximately every 6 months. The serum oestrodiol level remained persistently elevated despite the discontinuation of all exogenous estrogens, prompting a search for an alternative endogenous source. Tumour markers (HCG and ovarian marker) and magnetic resonance imaging of the abdomen and pelvis were normal. Her serum oestrodiol finally began to fall 18 months following initial presentation. Nearly 4 years after her last implant, the serum oestrodiol level still remains above the normal post-menopausal range (598 pmol/l).

This case shows that oestrogen implants may continue to release oestradiol for many years after initial implantation. The case adds to the evidence that it is important that implants are not replaced prematurely in an attempt to avoid recurrence of symptoms despite accumulation of oestradiol. It is important to advise women of this side-effect when counselling them regarding hormone replacement therapy.