Enclomiphene

Enclomiphene (also: Enclomifen) is the trans-isomer of the racemic compound clomiphene and acts as a selective estrogen receptor antagonist that blocks the negative feedback inhibition exerted by estrogens at the hypothalamus and pituitary, thereby stimulating endogenous gonadotropin secretion.

Pharmacological Basis and Distinction from Clomiphene

Clomiphene exists as a racemate composed of two geometric isomers: the cis-isomer zuclomiphene and the trans-isomer enclomiphene. Whereas zuclomiphene acts as a partial estrogen receptor agonist and is considered responsible for unwanted estrogenic side effects, enclomiphene exerts purely antagonistic activity at the estrogen receptors of the hypothalamus. This selective blockade removes the negative feedback inhibition on GnRH secretion, resulting in increased release of LH (luteinizing hormone) and FSH (follicle-stimulating hormone). This gonadotropin stimulation drives endogenous testosterone synthesis in the Leydig cells of the testes. Clinically, enclomiphene has been investigated in studies on secondary hypogonadism, where testosterone levels were normalized without suppressing sperm production — a key distinction from exogenous testosterone replacement therapy.

Relevance in the Context of Post-Cycle Therapy

In the research context of post-cycle therapy (PCT), enclomiphene is discussed as an alternative to classical clomiphene, as the absence of the partially agonistic zuclomiphene isomer may imply a more favorable side-effect profile. The hypothalamic-pituitary axis, suppressed by exogenous androgens or SARMs, can be reactivated through targeted estrogen receptor blockade. Enclomiphene offers the mechanistic advantage of pure antagonism without concurrent partial agonism. Human study data are available, though exclusively for specific medical indications; use in a sports context has not been regulatory reviewed.

Range & Selection

The range includes the following formulation:

Enclomiphene | 25 mg/Tab | 60 Tablets | Master Pharma – Oral tablet formulation containing 25 mg enclomiphene per unit in a pack of 60 tablets; suitable for research approaches requiring an extended oral administration sequence.