[7] His epiphyses were unfused, and there was evidence of still-occurring slow linear growth (for comparison, his height at 16 years of age was 178 cm).

[7] He reported no history of gender dysphoria, considered himself to have strong heterosexual interests, and had normal sexual function, including morning erections and nocturnal emissions.

[9] An in vitro assay of ERα-dependent gene transcription found that the EC50 for transactivation had been reduced by 240-fold relative to normal, non-mutated ERα, indicating an extreme reduction in the activity of the receptor.

[9] Clinical signs suggested a profile of complete estrogen insensitivity syndrome with a resemblance to ERα knockout mice.

[9] The patient presented with delayed puberty, including an absence of breast development (Tanner stage I) and primary amenorrhea, as well as intermittent pelvic pain.

[9] Examination revealed markedly enlarged ovaries with multiple hemorrhagic cysts as the cause of the lower abdominal pain.

[9] The patient had normal pubic hair development (Tanner stage IV) and severe facial acne, which could both be attributed to testosterone.

[9] In addition to her absence of breast development and areolar enlargement, the patient also appeared to show minimal widening of the hips and a lack of subcutaneous fat deposition, which is in accordance with the established role of estrogen and ERα in the development of female secondary sexual characteristics.

[6] The fact that the heterozygous parents and heterozygous sister were unaffected indicates that the disorder is transmitted in an autosomal recessive manner and that a single normal allele is sufficient to achieve normal puberty and fertility, which is consistent with what has been observed in ERα knockout mice.

[14] Levels of sex hormone-binding globulin (SHBG) were very low, which can be attributed to the absence of hepatic actions of estrogen.

[6] Impaired negative feedback by estrogen on the hypothalamic-pituitary-gonadal (HPG) axis would account for the elevated estradiol and gonadotropin levels in the siblings and for the ovarian enlargement and cyst formation in the sisters.

[6] The mutation caused a change from guanine to adenine at complementary DNA nucleotide 1181 (c.1181G>A) in the gene, which resulted in the substitution of a histidine for an arginine at residue 394 (p.Arg394His) in the helix H5 of the ligand-binding domain (LBD) of the ERα protein.

[6] Mutations involving the corresponding residue in the AR and MR have previously been associated with androgen insensitivity syndrome (AIS) and diminished sensitivity to mineralocorticoids, respectively.

[6] A group of other ERα agonists that included ethinylestradiol, diethylstilbestrol, tamoxifen, clomifene, and raloxifene were tested in their ability to promote transcriptional activity of the mutated ERα, but none of them were found to be more efficacious than estradiol in activating the mutated receptor and hence in overcoming the estrogen insensitivity of the siblings.

[6] As the sisters had very high, supraphysiological levels of circulating estradiol, the authors cautioned that it could not be ruled out that estradiol may have exerted some functional influence on their phenotypes via signaling through the ERβ and GPER (i.e., that not all of the observed phenotypes may have simply been due to loss of ERα signaling).

[16] In these so-called ERKO mice, different ERs can be disabled allowing to study the role of these receptors.

AIS is an X-linked recessive condition and thus carried over, by females, into future generations (although the most severe form, complete androgen insensitivity syndrome (CAIS), results in sterility, and hence cannot be passed on to offspring).

EIS is not compatible with reproduction, thus each occurrence in humans would have to be a de novo mutation and is not transmitted to offspring.