Enclomiphene vs hCG
Research Comparison

Research Overview

Enclomiphene and human chorionic gonadotropin (hCG) both act on the hypothalamic-pituitary-gonadal axis, but they are unrelated molecules that enter it at opposite ends. Enclomiphene, the trans (E) isomer of clomiphene, occupies estrogen receptors in the hypothalamus and blocks estrogen's negative feedback, so luteinizing hormone (LH) and follicle-stimulating hormone (FSH) rise (Rodriguez et al., 2016). hCG is a placental glycoprotein hormone that acts on the gonads through a receptor it shares with LH (Cole, 2010).

Enclomiphene vs hCG is therefore a question of where a study enters the axis: upstream feedback, read as LH and FSH, or the gonad itself. Disguised Alpha supplies enclomiphene as Enclomiphene Citrate capsules (12.5MG) and Liquid Enclomiphene (12.5MG/ML, 30ML bottle), and hCG as a lyophilized powder whose product name carries no strength; its 5000IU figure appears only in the certificate summary and on the vial in the product photo. All are for laboratory research use only.

Structure and Class

Enclomiphene is a chlorinated triphenylethylene with a diethylaminoethoxy side chain. PubChem lists the citrate (CID 6420009) as C32H36ClNO8 at 598.1 g/mol, the figures on the Enclomiphene Citrate product page, and the free base (CID 1548953) as C26H28ClNO at 406.0 g/mol. Its target is the estrogen receptor: in the immature rat uterus it was partially estrogenic with antiestrogenic properties, while its (Z) isomer zuclomiphene was predominantly estrogenic (Jordan et al., 1981).

hCG is a heterodimeric glycoprotein: a 92-residue alpha subunit almost identical to that of human LH and a 145-residue beta subunit, with sugar chains at two alpha and six beta positions (Morgan et al., 1975). Its molecular weight is about 36,000, of which 25 to 30% is sugar in regular hCG (Cole, 2010). The intact hormone has no single formula or PubChem compound record (CID), and preparations are usually labeled in units of activity (IU).

Its receptor, the LH/hCG receptor (LHCGR), is a cell-surface G protein-coupled receptor; cells engineered to express the rat luteal receptor bound hCG with high affinity and made more cyclic AMP (McFarland et al., 1989).

Side by Side

Research Context: Enclomiphene

In sheep pituitary cells, enclomiphene at 1 µM blocked estradiol's augmentation of the LH response to LHRH, while zuclomiphene acted as an estradiol agonist; earlier rat pituitary cultures had shown enclomiphene acting as an estrogen, a species difference the authors stressed (Huang and Miller, 1983). Model: sheep pituitary cells.

This trial came from the developer, Repros Therapeutics: a randomized, single-blind phase 2 study in 48 men with secondary hypogonadism compared three daily amounts of enclomiphene citrate with a transdermal testosterone comparator, sampling LH and total testosterone hourly for 24 hours. Enclomiphene raised LH and FSH while the comparator had the opposite effect, and the LH change persisted at least a week after exposure stopped (Wiehle et al., 2013). Model: a randomized trial in men.

The FDA advisory committee meeting on the new drug application, set for 3 November 2015, was canceled over concerns about bioanalytical method validation that arose late in the review (Rodriguez et al., 2016). In 2018 EnCyzix, an enclomifene capsule product, was refused EU marketing authorisation after the European Medicines Agency's committee noted that its studies did not look at symptoms and cited a risk of venous thromboembolism. Enclomiphene is approved by neither the FDA nor the EMA, and its manufacturer discontinued development in 2021 (Foster et al., 2026).

Research Context: hCG

In male rats, a low amount of hCG raised testicular LH receptor numbers slightly before they fell to about 30% of control; a 20-fold larger amount caused faster, more complete loss, inhibited the cyclic AMP response for up to 5 days and blocked the testosterone response to hCG in vitro for about 3 days (Hsueh et al., 1977). Model: male rats.

After a rapid intravenous bolus of purified hCG in healthy young men and women, the disappearance curve ran over 8 to 10 days, with rapid and slow half-lives of about 6 and 36 hours (Wehmann and Nisula, 1981). Model: healthy adult volunteers.

The FDA list of applications deemed to be biologics licenses on March 23, 2020 includes five chorionic gonadotropin drug products first approved between 1973 and 1976, plus choriogonadotropin alfa, first approved in 2000. That history covers those drug products only; Disguised Alpha's hCG is research material, not those products.

Choosing Between Them for a Research Question

For enclomiphene vs hCG, start with the level of the axis. Enclomiphene needs an intact hypothalamus and pituitary, because what it changes is their response to estradiol feedback (Rodriguez et al., 2016), so feedback and gonadotrope questions belong there. hCG binds LHCGR directly (McFarland et al., 1989), so questions about gonadal receptor signaling or steroid output can start at the gonad.

Then match the readout and time course. Enclomiphene studies read LH and FSH; the phase 2 LH change outlasted exposure by at least a week, beyond enclomiphene's half-life, cited as about 7 hours (Wiehle et al., 2013) or 10 hours (Rodriguez et al., 2016). hCG studies read the gonad, the hormone lingers for days (Wehmann and Nisula, 1981), and in rats a larger amount cut testicular LH receptor numbers (Hsueh et al., 1977).

Measurement differs too. An anti-doping laboratory characterized clomiphene, the isomer mixture that contains enclomiphene, and its metabolites by liquid chromatography with mass spectrometry (Mazzarino et al., 2013); such methods must separate the E and Z isomers, which share one mass. hCG is measured by immunoassay: a workshop on 27 monoclonal antibodies against hCG found 21 directed at the beta subunit and judged low cross-reactivity with LH mandatory (Berger et al., 2002). Enclomiphene is quantified by mass or moles and hCG in IU, so the two cannot be compared milligram for milligram.

Handling and Storage

The product pages list 15 to 25°C for sealed Enclomiphene Citrate capsules in the original container, away from moisture and direct light; 15 to 25°C for unopened Liquid Enclomiphene and 2 to 8°C once its seal is broken, protected from light and never frozen; and -20°C for lyophilized hCG as shipped and 2 to 8°C after reconstitution, protected from light, with freeze/thaw cycles avoided.

Let a sealed hCG vial reach room temperature before opening, add diluent slowly down the wall, swirl rather than shake, and split stock into single-use aliquots. For quantitative work, use each lot's certificate in the COA portal: the September 2026 certificate for capsule lot 543D reports 13.15 mg against the 12.5MG label, liquid lot EC01 reports 12.28 mg/mL against 12.5MG/ML, and the June 2026 hCG certificate (batch 35680) reports measured IU against the 5000IU label figure.

Questions Researchers Ask

Enclomiphene vs hCG: what is the difference?

Enclomiphene is a small-molecule SERM that blocks estrogen feedback in the hypothalamus, raising pituitary LH and FSH output (Rodriguez et al., 2016). hCG is a glycoprotein hormone that acts at the gonad through the receptor it shares with LH (Cole, 2010). One works upstream on feedback, the other on the gonad itself.

hCG vs enclomiphene: which one needs a working pituitary?

Enclomiphene: its axis effect is the LH and FSH the pituitary releases once estrogen feedback is blocked (Rodriguez et al., 2016). hCG binds the LH/hCG receptor on the gonad directly (McFarland et al., 1989).

Do enclomiphene and hCG act on the same receptor?

No. Enclomiphene binds the estrogen receptor, where it was a partial agonist with antiestrogenic properties in the rat uterus (Jordan et al., 1981). hCG binds LHCGR, a cell-surface G protein-coupled receptor (McFarland et al., 1989).

Are enclomiphene and hCG approved, or prohibited in sport?

Enclomiphene is approved by neither the FDA nor the EMA (Foster et al., 2026); US human chorionic gonadotropin drug products were first approved in 1973. The 2026 WADA Prohibited List names chorionic gonadotrophin (CG) in S2.2.1, for males, and covers SERMs under S4.2 "including, but not limited to" those listed; it names clomifene, not enclomiphene. Classes S2 and S4 are prohibited at all times.