Estriol

證據等級: L5

預測適應症: 2 個

Estriol: From Oestrogen Therapy to Amenorrhea

One-Sentence Summary

Estriol is a naturally occurring weak oestrogen historically used in hormone replacement therapy for menopausal symptoms and urogenital atrophy. The TxGNN model predicts it may be effective for Amenorrhea, with 3 clinical trials (all indirect evidence) and 13 publications currently identified in this direction. Notably, one interventional study directly demonstrates estriol’s ability to modulate LH secretion in functional hypothalamic amenorrhea patients.

Quick Overview

Item	Content
Original Indication	No approved indication recorded in Denmark (no marketing authorisation)
Predicted New Indication	Amenorrhea
TxGNN Prediction Score	99.18%
Evidence Level	L3 — Observational / interventional pilot studies and reviews
Denmark Market Status	Not marketed
Number of Marketing Authorisations	0
Recommended Decision	Hold

Why is This Prediction Reasonable?

Estriol (E3) is a weak, naturally occurring oestrogen with approximately one-tenth the binding affinity for oestrogen receptor alpha (ERα) compared to estradiol (E2). Unlike more potent oestrogens, estriol’s weak and short-acting properties mean it does not fully suppress the hypothalamic–pituitary–gonadal (HPG) axis. This pharmacological profile is potentially advantageous in the context of functional hypothalamic amenorrhea (FHA), where the goal is to restore—rather than replace—endogenous hormonal cycling.

In FHA, impaired pulsatile secretion of gonadotropin-releasing hormone (GnRH) leads to defective luteinising hormone (LH) and follicle-stimulating hormone (FSH) release, resulting in ovarian quiescence and amenorrhea. A key clinical study (Genazzani et al., 2012; PMID 22137494) directly demonstrated that estriol administration can modulate LH secretion patterns in FHA patients, suggesting that low-dose estriol may act as a neuroendocrine modulator capable of re-engaging the positive feedback mechanism at the hypothalamic–pituitary level.

However, estriol’s short half-life and lack of active metabolites limit its suitability as a sustained hormone replacement therapy. The TxGNN prediction score of 99.18% is high, but the current clinical evidence base remains limited to small interventional studies and mechanistic reviews. No completed randomised controlled trial has specifically evaluated estriol monotherapy for amenorrhea as a primary endpoint.

Clinical Trial Evidence

Trial Number	Phase	Status	Enrolment	Key Findings
NCT04090957	Phase 3	Completed	1,015	Estetrol (E4), not estriol (E3): evaluated E4 15/20 mg vs placebo for vasomotor symptoms in postmenopausal women. Indirect class evidence only.
NCT04209543	Phase 3	Completed	1,570	Estetrol (E4), not estriol (E3): confirmatory trial of E4 for vasomotor symptoms. Same class but distinct pharmacology (NEST mechanism). Not directly applicable.
NCT04487392	Phase 2	Withdrawn	0	Photobiomodulation for vulvovaginal atrophy in postmenopausal women. Trial withdrawn with no enrolment; no data generated.

Important note: All three identified clinical trials have low direct relevance (Grade C). The two completed Phase 3 trials investigated estetrol (E4), a distinct oestrogen with different receptor pharmacology, not estriol (E3). No registered clinical trial was identified that directly evaluates estriol for the treatment of amenorrhea.

Literature Evidence

PMID	Year	Type	Journal	Key Findings
22137494	2012	Clinical Study (interventional)	Fertility and Sterility	Direct evidence: Estriol administration modulates LH secretion in women with functional hypothalamic amenorrhea (FHA).
37371858	2023	Review / Perspective	Biomedicines	Low-dose oestrogens as neuroendocrine modulators in FHA; discusses triggering of positive feedback mechanisms on GnRH pulsatility.
16526238	2005	Clinical Study	Medicinski Pregled	Effects of oestro-progestagens on lipid and hormonal profiles in women with premature primary ovarian failure (hypergonadotropic amenorrhea).
2949864	1986	Observational	Zhong Xi Yi Jie He Za Zhi	Observations on gonadal function changes in women with amenorrhea and oligomenorrhea.
4102186	1971	Case Report	The Lancet	Endocrinological findings in two patients with premature ovarian failure.
14194444	1964	Clinical Trial	J Obstet Gynaecol Br Commonw	Effect of pituitary/urinary FSH and hCG on patients with idiopathic secondary amenorrhea.
13931724	1963	Basic Science Review	J Clin Endocrinol Metab	Mechanism of action of anti-ovulatory compounds, including oestrogen class effects.
7026111	1981	Review	Clin Obstet Gynecol	Neoplasia and hormonal contraception — background on oestrogen-related effects.
5935707	1966	Case Report/Series	Am J Obstet Gynecol	Prolonged gynaecologic and endocrine manifestations following medroxyprogesterone acetate administration during pregnancy.
4307531	1969	Laboratory Study	Fertility and Sterility	Comparative effects of oestrogens (including estriol) on amylase levels of cervical mucus.

Denmark Market Information

Estriol does not currently hold a marketing authorisation in Denmark (neither national Laegemiddelstyrelsen nor centralised EMA authorisation identified in this dataset). No product is marketed under this active substance in the Danish market.

Note: Estriol-containing products are available in several other European countries (e.g., vaginal creams, pessaries). Availability through the special access scheme (udleveringstilladelse) or magistral preparation should be explored if clinical use is considered.

Safety Considerations

Please refer to the approved Summary of Product Characteristics (SmPC) for safety information. No specific warnings, contraindications, or drug–drug interactions were available in the evidence pack for estriol.

Conclusion and Next Steps

Decision: Hold

Rationale: While the TxGNN prediction score is very high (99.18%) and a plausible mechanistic rationale exists—supported by one directly relevant interventional study (PMID 22137494) showing estriol modulates LH secretion in FHA—the overall evidence base remains insufficient for clinical translation. No completed RCT has evaluated estriol specifically for amenorrhea, the identified clinical trials concern a different compound (estetrol), and estriol is not currently marketed in Denmark.

To proceed, the following is needed:

Mechanism of action (MOA) data: Complete pharmacodynamic profiling of estriol’s effects on the HPG axis, including dose–response relationships
Safety profile: Obtain full SmPC-equivalent safety data, including contraindications (e.g., oestrogen-dependent tumours, thromboembolic history) and drug interactions
Market access assessment: Evaluate whether estriol can be obtained in Denmark via special access, cross-border supply, or magistral preparation
Clinical study design: A prospective, randomised, placebo-controlled pilot trial of low-dose estriol in FHA patients, with LH pulsatility and return of menses as primary endpoints
Regulatory pathway: Determine whether an off-label use or compassionate access pathway would be appropriate given the current evidence level (L3)
Disclaimer

This content is for research purposes only and does not constitute medical advice. Clinical validation is required before any clinical application.