Toremifene
A triphenylethylene SERM closely related to tamoxifen, approved for metastatic breast cancer. In PED contexts it is used to blunt estrogenic side effects and to restart the HPTA during post-cycle therapy, raising LH, FSH and endogenous testosterone.
01 Overview
Toremifene (Fareston) is a chlorinated analogue of tamoxifen developed for oestrogen-receptor-positive breast cancer. It acts as a mixed agonist/antagonist at the oestrogen receptor, antagonising it in breast tissue while retaining agonist activity at the hypothalamus and pituitary.
Among steroid users it is favoured over tamoxifen by some because it appears to have less effect on IGF-1 suppression and a similar gonadotropin-stimulating profile. It is used both to prevent gynecomastia during a cycle and, more commonly, as a PCT agent to accelerate recovery of the gonadal axis.
02 Mechanism
Selective oestrogen receptor modulator: blocks oestrogen negative feedback at the hypothalamus/pituitary, increasing GnRH pulses, LH and FSH, and thereby endogenous testosterone; antagonises oestrogen in breast tissue.
03 Dosing
| Tier | Dose | Route | Notes |
|---|---|---|---|
| Gyno control | 30 mg/day | Oral | On-cycle to prevent breast tissue growth. |
| PCT | 30–60 mg/day | Oral | Typical off-label restart dosing, tapered over 3-4 weeks. |
| Breast cancer | 60 mg/day | Oral | Licensed oncology dose. |
04 Effects
| Effect | Magnitude | Evidence | |
|---|---|---|---|
| Raised endogenous testosteroneBlocks central oestrogen feedback, stimulating gonadotropin release and testicular steroidogenesis. | LH/FSH and total T increase | Clinical | |
| Reduced gynecomastia riskAntagonises oestrogen receptors in breast tissue. | Prevents/slows breast tissue growth | Observational |
05 Side effects
| Effect | Severity | Frequency | Evidence | Countermeasures |
|---|---|---|---|---|
| Hot flashesVasomotor flushing from oestrogen antagonism. | Mild | Common | Clinical | |
| QT prolongationDose-dependent prolongation of the QT interval, a class warning distinguishing toremifene from tamoxifen. | Severe | Uncommon but labelled | Clinical | |
| Venous thromboembolismSERM class risk of clot formation. | Severe | Rare | Clinical |