ESPE Abstracts

Introduction: Rare mutations of the ESR1gene, encoding the estrogen receptor alpha (ERα), have been shown to cause estrogen resistance in humans. To date, there are no effective therapeutic options. We report the case of a new inactivating mutation of ERα and provide evidence for a partial restoration of biological effects of estrogen.

Methods: We performed clinical and biological phenotyping of the index case and sequenced the ESR1gene. Structural and functional studies were performed in vitro in the presence of different ligands using two cellular models: HeLa transfected with the ERE-β-globin Luc+ vector (stable clones) and HepG2 transiently co-transfected with the C3 Luc reporter. A therapeutic trial was conducted with the administration of high doses of ethinyl-estradiol (EE, 50-100 μg/day) per os for 3 months.

Results: We describe a 20-year-old female, with primary amenorrhea and lack of breast development. Pelvic MRI revealed a rudimentary uterus and polycystic ovaries. The patient presented with tall stature (180 cm), continuous linear growth, delayed bone age (12 years) and severe osteoporosis (BMD −4 S.D.). Hormonal profile revealed LH 40 IU/l, FSH 44 IU/l, E2 1670 pmol/l (reference 220–400). Her BMI was 28 kg/m² with increased abdominal adiposity (DXA: trunk/limb fat ratio 1.3) and discrete hepatic fat overload (MRI spectroscopy). Metabolic profile showed severe insulin resistance (HOMA-IR 11.5), decreased insulin sensitivity (SI-OGTT Stumvoll: −0.05), increased insulinogenic index ΔIns30/ΔGluc30 (7.3), and hyperleptinemia (75 ng/ml) with normolipidemia. Sequencing of the ESR1 gene identified a new homozygous variant (p.Met543Thr) in the ligand binding domain (activation function-2, AF2). Functional studies in vitro revealed a slight decrease in the affinity of the M543T variant for estradiol; a dramatic decrease in transcriptional activity involving AF2; and the possibility of partial restoration of the transcriptional activity in the presence of high concentrations of ligand. Therapeutic trial with a high dose of EE improved the patient’s insulin sensitivity (HOMA-IR: 5.9, SI-OGTT Stumvoll: 0.02, ΔIns30/ΔGluc30: 0.8), decreased circulating leptin (36 ng/ml) and increased several estrogen-regulated liver proteins; with no effect on the endometrium and bone.

Discussion: A new ERα receptor inactivating mutation, located in the ligand binding domain (p.Met543Thr), is responsible for a dramatic decrease in the AF2 (ligand-dependent) transcriptional activity. The structural and functional study of the receptor indicated the possibility of partial restoration of estrogen effects. The therapeutic trial with high doses of EE supports this hypothesis showing a marked improvement of insulin sensitivity.