Altrenogest
Altrenogest (Regu-Mate) is a potent orally active progestin used to control the estrous cycle in mares and to synchronise breeding in swine. It is a 19-nortestosterone-derived progestogen with no anabolic bodybuilding role; it appears in doping and residue contexts and is hazardous through skin contact for handlers.
01 Overview
Altrenogest is a trenbolone-related 19-nor allyl-substituted progestin, structurally in the trienolone/nortestosterone family but functionally a progestagen. In equine and porcine reproduction it maintains luteal-phase progestin tone to suppress estrus and time ovulation.
Although it shares a skeleton with anabolic 19-nor steroids, its dominant progestogenic activity makes it useless and counterproductive as a PED. It is notable as a handling hazard (readily absorbed through skin, contraindicated in pregnant women) and as an anti-doping analyte in equine and human sport.
02 Mechanism
Strong progesterone-receptor agonist derived from the 19-nortestosterone/allyltrenbolone skeleton; maintains progestational tone that suppresses the hypothalamic-pituitary-gonadal axis and blocks estrus.
03 Dosing
| Tier | Dose | Route | Notes |
|---|---|---|---|
| Mare estrus suppression (veterinary) | 22–44 mg/day | Oral | Equine dose (~0.044 mg/kg); not a human recommendation |
Ester comparison
| Ester | Half-life | Injection freq. | Testosterone by mass |
|---|
04 Effects
| Effect | Magnitude | Evidence | |
|---|---|---|---|
| Estrus suppression / cycle controlReliably suppresses estrus in mares and synchronises cycles in swine. | Clinical | ||
| Progestational maintenanceMaintains luteal-phase progestin tone for breeding management. | Clinical |
05 Side effects
| Effect | Severity | Frequency | Evidence | Countermeasures |
|---|---|---|---|---|
| Transdermal absorption hazardReadily absorbed through human skin; can disrupt the menstrual cycle and is contraindicated in pregnancy. | Moderate | Handler risk | Observational | |
| Progestogenic suppressionAs a strong progestin it would suppress gonadal function and libido with no anabolic benefit. | Moderate | Predicted in humans | Preclinical |