Stimulation of Leydig and Sertoli cellular secretory function by anti-oestrogens: Tamoxifen

Tamoxifen is a selective oestrogen receptor modulator (SERM). SERMs act on oestrogen receptors to inhibit oestradiol mediated negative feedback on the hypothalamic-pituitary-gonadal (HPG) axis, thereby upregulating gonadotrophin secretion and release from the pituitary. Hence, Tamoxifen is used to upregulate activation of the HPG axis in the treatment of male-factor infertility. However, due to a lack of robust evidence, Tamoxifen has not been FDA approved for use in male-factor infertility and so its use is currently off-label. In this study, we performed a literature search of the OVID medline database and identified 37 studies describing the effects of tamoxifen which we then reviewed. Evidence suggests Tamoxifen effectively increases androgen levels and sperm concentrations in males with idiopathic oligozoospermia. Evidence for increased motility and pregnancy rates in these patients is less conclusive. Further randomised control trials are needed to elucidate the safety of Tamoxifen combination therapies and their efficacy in improving pregnancy rates.

Retained products of conception in hysteroscopy in a patient with breast cancer on tamoxifen

Tamoxifen is a selective oestrogen receptor modulator widely used in breast cancer treatment, with good survival rates. Its partial agonist action on other tissues such as the uterus, however, promotes the development of endometrial hyperplasia and cancer. It appears that tamoxifen does not alter the age of menopause and women may still get pregnant while on tamoxifen. We present the case of a 47-year-old Chinese woman with breast cancer on tamoxifen, who presented with one episode of heavy per vaginal bleeding after 2 years of amenorrhoea. Her urine pregnancy test was negative and the ultrasound scan was suspicious for malignancy. She underwent a hysteroscopic evaluation for abnormal bleeding on tamoxifen. Histopathology confirmed products of conception. This case illustrates the importance of understanding the rise and decline of human chorionic gonadotropin in pregnancy, as well as the pivotal role of contraception despite having amenorrhoea on tamoxifen.

Oestrogenic action of neonatal tamoxifen on the hypothalamus and reproductive system in female mice

Tamoxifen, a selective oestrogen receptor modulator, is widely used for both the treatment and prevention of breast cancer in women; however, it is known to have adverse effects in the female reproductive system. Growing evidence suggests that oestrogen-sensitive neuron populations of the anteroventral periventricular (AVPV) nucleus and arcuate (ARC) nucleus, especially kisspeptin neurons, play a pivotal role in the timing of puberty onset and reproductive function. The aim of the present study was to evaluate whether neonatal exposure to tamoxifen affects oestrogenic actions in the brain and reproductive function in mice. On 1 to 5 postnatal days, female pups were injected subcutaneously with sesame oil (sham), oestradiol benzoate (EB; 20 µg kg–1), tamoxifen (0.4 mg kg–1) or EB+tamoxifen. Control mice received no treatment. Mice in the EB, tamoxifen and tamoxifen+EB groups exhibited advanced vaginal opening, disrupted oestrous cycles and a decreased follicular pool. Conversely, in these groups, there was a reduction in kisspeptin (Kiss1) mRNA expression, the neuronal density of AVPV and ARC nuclei and LH and oestradiol concentrations in the serum. The results of the present study confirm oestrogenic actions of tamoxifen in the brain and reproductive system. In addition, we show, for the first time, that tamoxifen has oestrogenic effects on the oestrogen-sensitive hypothalamic AVPV and ARC nuclei controlling the reproductive axis in female mice.

In vivo activation of gene transcription via oestrogen response elements by a raloxifene analogue

Raloxifene is a selective oestrogen receptor modulator with tissue-specific effects. The mechanisms behind the effects of raloxifene are partly unclear, and the aim of the present study was to investigate whether raloxifene can activate the classical oestrogen-signalling pathway in vivo in three known oestrogen-responsive organs, uterus (reproductive organ), bone (non-reproductive organ) and thymus (immune organ). For this purpose, we have used reporter mice with a luciferase gene under control of oestrogen-responsive elements (EREs), enabling detection of in vivo activation of gene transcription via the classical oestrogen pathway. Three-month-old ovariectomized ERE-luciferase mice were treated with the raloxifene analogue (LY117018), oestradiol (OE2) or vehicle for 3 weeks. Luciferase activation was measured in bone, uterus and thymus, and compared to bone parameters, and uterus and thymus weights. The raloxifene analogue affected bone mineral density (BMD) to the same extent as OE2, and both treatments resulted in increased luciferase activity in bone. As expected, OE2 treatment resulted in increased uterus weight and increased uterine luciferase activity, while the effect of LY117018 on uterus weight and luciferase activity was modest and significantly lower than the effect of OE2. LY117018 and OE2 treatment resulted in similar luciferase activation in thymus. However, only OE2 treatment resulted in thymic atrophy, while no effect on thymus weight was seen after LY117018 treatment. In summary, the raloxifene analogue LY117018 can activate the classical oestrogen pathway in bone, uterus and thymus in vivo, and this activation is associated with BMD and uterus weight, but not thymus weight.