Congenital Adrenal Hyperplasia (Chapter 570.1)

This is the most common cause of genital ambiguity and of 46,XX DSD. Females with the 21-hydroxylase and 11-hydroxylase defects are the most highly virilized, although minimal virilization also occurs with the type II 3β-hydroxysteroid dehydrogenase defect (see Fig. 582-1). Salt losers tend to have greater degrees of virilization than do non–salt-losing patients. Masculinization may be so intense that a complete penile urethra results, and the condition may mimic a male with bilateral cryptorchidism.

Aromatase Deficiency

In genotypic females, the rare condition of aromatase deficiency during fetal life leads to 46,XX DSD and results in hypergonadotropic hypogonadism at puberty because of ovarian failure to synthesize estrogen (see Fig. 568-1).

Two 46,XX infants had enlargement of the clitoris and posterior labial fusion at birth. In 1 instance, maternal serum and urinary levels of estrogen were very low and serum levels of androgens were high. Cord serum levels of estrogen were also extremely low, but those of androgen were elevated. The 2nd patient also had virilization of unknown cause since birth, but the aromatase deficiency was not diagnosed until 14 yr of age, when she had further virilization and failed to go into puberty. At that time, she had elevated levels of gonadotropins and androgens but low estrogen levels, and ultrasonography revealed large ovarian cysts bilaterally. These 2 patients demonstrate the important role of aromatase in the conversion of androgens to estrogens. Additional female and male patients with aromatase deficiency due to mutations in the P450_arom (CYP19) gene are known. Two siblings were described. The 28 yr old XY proband was 177.6 cm tall (+2.5 SD) after having received hormonal replacement therapy; her 24 yr old brother was 204 cm tall (+3.7 SD), and had a bone age of 14 yr. Low-dose estradiol replacement, carefully adjusted to maintain normal age-appropriate levels, may be indicated for affected females even prepubertally.

Glucocorticoid Receptor Gene Mutation

A 9 yr old girl with 46,XX disorder of sexual development, thought to be due to 21-hydroxylase deficiency (congenital adrenal hyperplasia) since the age of 5 yr, had elevated cortisol levels both at baseline and after dexamethasone, hypertension, and hypokalemia, suggestive of the diagnosis of generalized glucocorticoid resistance. A novel homozygous mutation in exon 5 of the glucocorticoid receptor was demonstrated. In this Brazilian family, the condition was autosomal recessive.

POR, cytochrome P450 oxidoreductase, encoded by a gene on 7q11.2, is a cofactor implicated in combined P450C17 and P450C21 steroidogenic defects. Girls are born with ambiguous genitalia, but the virilization does not progress postnatally and androgen levels are normal or low. Boys may be born undervirilized. Both may exhibit bony abnormalities seen in Antley-Bixler syndrome (ABS). Conversely, in a series of ABS patients, those with ambiguous genitalia and disordered steroidogenesis had POR deficiency. Those without genital ambiguity with normal steroidogenesis had fibroblast growth factor receptor 2 (FGFR2) mutations. The cardinal features of ABS include craniosynostosis, severe midface hypoplasia, proptosis, choanal atresia/stenosis, frontal bossing, dysplastic ears, depressed nasal bridge, radiohumeral synostosis, long bone fractures and femoral bowing, and urogenital abnormalities.

Virilizing Maternal Tumors

Rarely, the female fetus has been virilized during fetal life by a maternal androgen-producing tumor. In a few cases, the lesion was a benign adrenal adenoma, but all others were ovarian tumors, particularly androblastomas, luteomas, and Krukenberg tumors. Maternal virilization may be manifested by enlargement of the clitoris, acne, deepening of the voice, decreased lactation, hirsutism, and elevated levels of androgens. In the infant, there is enlargement of the clitoris of varying degrees, often with labial fusion. Mothers of children with unexplained 46,XX DSD should undergo physical examination and measurements of their own levels of plasma testosterone, dehydroepiandrosterone sulfate, and androstenedione.

Administration of Androgenic Drugs to Women during Pregnancy

Testosterone and 17-methyltestosterone have been reported to cause 46,XX DSD in some instances. The greatest number of cases has resulted from the use of certain progestational compounds for the treatment of threatened abortion. These progestins have been replaced by nonvirilizing ones.

Infants with virilization and 46,XX chromosomes and caudal anomalies have been reported for whom no virilizing agent could be identified. In such instances, the disorder is usually associated with other congenital defects, particularly of the urinary and gastrointestinal tracts. Y-specific DNA sequences, including SRY, are absent. In 1 case, a scrotal raphe and elevated testosterone levels were found, but the cause remains unknown.

Defects in Testicular Differentiation

The 1st step in male differentiation is conversion of the indifferent gonad into a testis. In the XY fetus, if there is a deletion of the short arm of the Y chromosome or of the SRY gene, male differentiation does not occur. The phenotype is female; müllerian ducts are well developed because of the absence of AMH, but gonads consist of undifferentiated streaks. By contrast, even extreme deletions of the long arm of the Y chromosome (Yq-) have been found in normally developed males, most of whom are azoospermic and have short stature. This indicates that the long arm of the Y chromosome normally has genes that prevent these manifestations. In many syndromes in which the testes fail to differentiate, Y chromosomes are morphologically normal.

Defects in Testicular Hormones

Five genetic defects have been delineated in the enzymatic synthesis of testosterone by fetal testis, and a defect in Leydig cell differentiation has been described. These defects produce 46,XY males with inadequate masculinization (see Fig. 576-1). Because levels of testosterone are normally low before puberty, an hCG stimulation test may be needed in children to assess the ability of the testes to synthesize testosterone.

Defects in Androgen Action

In the following group of disorders, fetal synthesis of testosterone is normal and defective virilization results from inherited abnormalities in androgen action.

5α-Reductase Deficiency

Decreased production of dihydrotestosterone (DHT) in utero results in marked ambiguity of external genitalia of affected males. Biosynthesis and peripheral action of testosterone are normal.

The phenotype most commonly associated with this condition results in boys who have a small phallus, bifid scrotum, urogenital sinus with perineal hypospadias, and a blind vaginal pouch (Fig. 582-3). Testes are in the inguinal canals or labioscrotal folds and are normal histologically. There are no müllerian structures. Wolffian structures—the vas deferens, epididymis, and seminal vesicles—are present. Most affected patients have been identified as females. At puberty, virilization occurs; the phallus enlarges, the testes descend and grow normally, and spermatogenesis occurs. There is no gynecomastia. Beard growth is scanty, acne is absent, the prostate is small, and recession of the temporal hairline fails to occur. Virilization of the Wolffian duct is caused by the action of testosterone itself, although masculinization of the urogenital sinus and external genitals depends on the action of DHT during the critical period of fetal masculinization. Growth of facial hair and of the prostate also appears to be DHT dependent.

Figure 582-3 5α-Reductase deficiency.

(From Wales JKH, Wit JM, Rogol AD: Pediatric endocrinology and growth, ed 2, Philadelphia, 2003, Elsevier/Saunders, p 165.)

The adult height reached is close to that of the father and other male siblings. There is significant phenotypic heterogeneity. This has led to a classification of such patients into 5 types of steroid 5α-reductase deficiency (SRD).

Several different gene defects leading to SRD have been identified in the 5α-reductase type 2 gene, located on the short arm of chromosome 2, in patients from throughout the world. Familial clusters have been reported from the Dominican Republic, Turkey, Papua New Guinea, Brazil, Mexico, and the Middle East. There is no reliable correlation between genotype and phenotype.

The disorder is inherited as an autosomal recessive trait but is limited to males; normal homozygous females with normal fertility indicate that in females DHT has no role in sexual differentiation or in ovarian function later in life. The clinical diagnosis should be made as early as possible in infancy. It is important to distinguish this from partial androgen insensitivity syndrome (PAIS), as patients with PAIS are far less sensitive to androgen than are patients with SRD. The biochemical diagnosis of SRD is based on finding normal serum testosterone levels, normal or low DHT levels with markedly increased basal and especially hCG-stimulated testosterone : DHT ratios (>17), and high ratios of urinary etiocholanolone to androsterone. Children with androgen insensitivity have normal hepatic 5α reduction and, thus, a normal ratio of tetrahydrocortisol to 5α-tetrahydrocortisol, as opposed to those with SRD.

It is important to note that most but not all children with SRD reared as females in childhood have changed to male around the time of puberty. It appears that exposures to testosterone in utero, neonatally, and at puberty have variable contributions to the formation of male gender identity. Much more needs to be learned about the influences of hormones such as androgens as well as the influences of cultural, social, psychologic, genetic, and other biologic factors in gender identity and behavior. Infants with this condition should be reared as boys whenever practical. Treatment of male infants with DHT results in phallic enlargement.

Androgen Insensitivity Syndromes

The AISs are the most common forms of male DSD, occurring with an estimated frequency of 1/20,000 genetic males. This group of heterogeneous X-linked recessive disorders is due to more than 150 different mutations in the androgen receptor gene, located on Xq11-12: single point mutations resulting in amino acid substitutions or premature stop codons, frameshift and premature terminations, gene deletions, and splice site mutations.

Clinical Manifestations

The clinical spectrum of patients with AISs, all of whom have a 46,XY chromosomal complement, range from phenotypic females (in complete AIS) to males with various forms of ambiguous genitalia and undervirilization (partial AIS, or clinical syndromes such as Reifenstein syndrome) to phenotypically normal-appearing males with infertility. In addition to normal 46,XY chromosomes, the presence of testes and normal or elevated testosterone and LH levels are common to all such children (Figs. 582-4 and 582-5).

Figure 582-4 A, Partial androgen insensitivity with descended testes in bifid labioscrotal folds. B, Less severe partial androgen insensitivity with severe hypospadias and maldescent of testes.

(From Wales JKH, Wit JM, Rogol AD: Pediatric endocrinology and growth, ed 2, Philadelphia, 2003, Elsevier/Saunders, p 165.)

Figure 582-5 Partial androgen insensitivity syndrome at adolescence, male sex of rearing. Note gynecomastia from peripheral aromatase conversion of testosterone to estrogen. Abundant pubic hair implies only partial resistance.

(From Wales JKH, Wit JM, Rogol AD: Pediatric endocrinology and growth, ed 2, 2003, Philadelphia, Elsevier/Saunders, p 165.)

In complete AIS, an extreme form of failure of virilization, genetic males appear female at birth and are invariably reared accordingly. The external genitalia are female. The vagina ends blindly in a pouch, and the uterus is absent due to the normal production and effect of AMH by the testes. In about one third of patients, unilateral or bilateral fallopian tube remnants are found. The testes are usually intra-abdominal but may descend into the inguinal canal; they consist largely of seminiferous tubules. At puberty, there is normal development of breasts, and the habitus is female, but menstruation does not occur and sexual hair is absent. Adult heights of these women are commensurate with those of normal males despite profound congenital deficiency of androgenic effects.

The testes of affected adult patients produce normal male levels of testosterone and DHT. Failure of normal male differentiation during fetal life reflects defective response to androgens at that time. The absence of androgenic effects is caused by a striking resistance to the action of endogenous or exogenous testosterone at the cellular level.

Prepubertal children with this disorder are often detected when inguinal masses prove to be testes or when a testis is unexpectedly found during herniorrhaphy in a phenotypic female. About 1-2% of girls with an inguinal hernia prove to have this disorder. In infants, elevated gonadotropin levels should suggest the diagnosis. In adults, amenorrhea is the usual presenting symptom. In prepubertal children, the condition must be differentiated from other types of XY under virilized males in which there is complete feminization. These include XY gonadal dysgenesis (Swyer syndrome), true agonadism, Leydig cell aplasia including LH receptor defects, and 17-ketosteroid reductase deficiency; all these conditions, unlike complete AIS, are characterized by low levels of testosterone as neonates and during adult life and by failure to respond to hCG during the prepubertal years. Although patients with complete AIS have unambiguously female external genitals at birth, those with partial AIS have a wide variety of phenotypic presentations ranging from perineoscrotal hypospadias, bifid scrotum, and cryptorchidism to extreme under virilization appearing as clitoromegaly and labial fusion. Some forms of partial AIS have been known as specific syndromes. Patients with Reifenstein syndrome have incomplete virilization characterized by hypogonadism, severe hypospadias, and gynecomastia (see Fig. 582-5). Gilbert-Dreyfus and Lubs are additional syndromes classified as partial AIS. In all cases, abnormalities in the androgen receptor gene have been identified.

Diagnosis

The diagnosis of patients with partial AIS may be particularly difficult in infancy. The postnatal surge in testosterone and LH is diminished in those with complete AIS (CAIS) but not in those with partial AIS (PAIS). In some, especially those sufficiently virilized in infancy, the diagnosis is not suspected until puberty when there is inadequate virilization with lack of facial hair or voice change and the appearance of gynecomastia. Azoospermia and infertility are common. Increasingly, androgen receptor defects are being recognized in adults who have a small phallus and testes and infertility. A single-amino-acid substitution in the androgen receptor was reported in a large Chinese family in whom some affected members were fertile while others had gynecomastia and/or hypospadias. IGF2 and IGFBP2 but not IGFBP3 production by genital skin fibroblasts is decreased in CAIS compared with normal genital skin fibroblasts, suggesting a possible role for the IGF system in modulating androgen action.

Treatment and Prognosis

In patients with CAIS whose sexual orientation is unambiguously female, the testes should be removed as soon as they are discovered. Laparoscopic removal of Y chromosome–bearing gonads has been performed in patients with AIS and in those with gonadal dysgenesis. In one third of patients, malignant tumors, usually seminomas, develop by 50 yr of age. Several teenage girls have acquired seminomas. Replacement therapy with estrogens is indicated at the age of puberty.

Normal breasts develop in affected girls who have not had their testes removed by the age of puberty. In these individuals, production of estradiol results from aromatase activity on testicular testosterone. The absence of androgenic activity also contributes to the feminization of these women.

The psychosexual and surgical management of patients with partial AIS is extremely complex and depends in large part on the presenting phenotype. Osteopenia is recognized as a late feature of AIS.

Molecular analyses have suggested that phenotype may depend in part on somatic mosaicism of the androgen receptor gene. This was based on the case of a 46,XY patient who had a premature stop codon in exon 1 of the AR gene but who also had evidence of virilization (pubic hair and clitoral enlargement) explained by the discovery of the wild-type alleles on careful examination of the sequencing gel. The presence of mosaicism shifts the phenotype to a higher degree of virilization than expected from the genotype of the mutant allele alone.

Genetic counseling is difficult in families with androgen receptor gene mutation. In addition to lack of genotype-phenotype correlations, there is a high rate (27%) of de novo mutations in families.

Sex hormone–binding globulin reduction after exogenous androgen administration (stanozolol) has been shown to correlate with the severity of the receptor defect and may become a useful clinical tool. Successful therapy with supplemental androgens has been reported in patients with partial AIS and various mutations of the androgen receptor in the DNA-binding domain and the ligand-binding domain.

Mutated androgen receptors are also reported in patients with spinal and bulbar muscular atrophy in whom clinical manifestations including testicular atrophy, infertility, gynecomastia, and elevated LH, FSH, and estradiol levels usually manifest between the 3rd and 5th decades of life. Androgen receptor mutations have also been described in patients with prostate cancer.

Undetermined Causes

Other XY undervirilized males display great variability of the external and internal genitalia and various degrees of phallic and müllerian development. Testes may be histologically normal or rudimentary, or there may only be 1. Even the newer techniques may find no recognized cause in a up to 50% of children with 46,XY DSD. Some ambiguity of the genitalia is associated with a wide variety of chromosomal aberrations, which must always be considered in the differential diagnosis, the most common being the 45,X/46,XY syndrome (Chapter 580.1). It may be necessary to karyotype several tissues to establish mosaicism. Other complex genetic syndromes, many resulting from single gene mutations, are associated with varying degrees of ambiguity of the genitalia, particularly in the male. These entities must be identified on the basis of the associated extragenital malformations.

Smith-Lemli-Opitz syndrome is an autosomal recessive disorder caused by mutations in the sterol Δ7-reductase gene located on chromosome 11q12-q13. It is characterized by prenatal and postnatal growth retardation, microcephaly, ptosis, anteverted nares, broad alveolar ridges, syndactyly of the 2nd-3rd toes, and severe mental retardation (Chapter 80.3). Its incidence is 1/20,000 to 1/60,000; 70% are male. Genotypic males usually have genital ambiguity and, occasionally, partial sex reversal with female genital ambiguity or complete sex reversal with female external genitals. Müllerian duct derivatives are usually absent. Affected 46,XX patients have normal genitalia. Two types of Smith-Lemli-Opitz syndrome have been recognized. The classical form (type I) described earlier and the acrodysgenital syndrome, which is usually lethal within 1 yr and is associated with severe malformations, postaxial polydactyly, and extremely abnormal external genitalia (type II). Pyloric stenosis is associated with Smith-Lemli-Opitz syndrome type I and Hirschsprung disease with type II. Cleft palate, skeletal abnormalities, and 1 case of a lipoma of the pituitary gland have been seen in type II cases. Some authors believe in a spectrum of disease severity rather than in the above classification. Low plasma cholesterol with elevated 7-dehydrocholesterol, its precursor, are found in types 1 and 2, and the levels do not correlate with severity. Maternal apolipoprotein E values do seem to correlate with severity. The most common prenatal expression of Smith-Lemli-Opitz syndrome is intrauterine growth retardation (see Chapter 80.3 for treatment).

46,XY DSD subjects also have been described in siblings with the α-thalassemia/mental retardation syndrome.

Diagnosis and Management

In the neonate, ambiguity of the genitals requires immediate attention to decide on the sex of rearing as early in life as possible. The family of the infant needs to be informed of the child’s condition as early, completely, compassionately, and honestly as possible. Caution must be used to avoid feelings of guilt, shame, and discomfort. Guidance needs to be provided to alleviate both short-term and long-term concerns and to allow the child to grow up in a completely supportive environment. The initial care is best provided by a team of professionals that include neonatologists and pediatric specialists, endocrinologists, radiologists, urologists, psychologists, and geneticists, all of whom remain focused foremost on the needs of the child. Management of the potential psychologic upheaval that these disorders can generate in the child or the family is of paramount importance and requires physicians and other health care professionals with sensitivity, training, and experience in this field.

While awaiting the results of chromosomal analysis, pelvic ultrasonography is indicated to determine the presence of a uterus and ovaries. Presence of a uterus and absence of palpable gonads usually suggests a virilized XX female. A search for the source of virilization should be undertaken; this includes studies of adrenal hormones to rule out varieties of congenital adrenal hyperplasia, and studies of androgens and estrogens occasionally may be necessary to rule out aromatase deficiency. Virilized XX females are generally (but not always) reared as females even when highly virilized.

The absence of a uterus, with or without palpable gonads, almost always indicates an under virilized male and an XY karyotype. Measurements of levels of gonadotropins, testosterone, AMH, and DHT are necessary to determine whether testicular production of androgen is normal. Under virilized males who are totally feminized may be reared as females. Certain significantly feminized infants, such as those with 5α-reductase deficiency, may be reared as males because these children virilize normally at puberty. Sixty percent of individuals with 5α-reductase deficiency assigned as female in infancy live as males. An infant with a comparable degree of feminization resulting from an androgen receptor defect, such as CAIS, is best reared as a female.

When receptor disorders are suspected in the XY male with a small phallus (micropenis), a course of 3 monthly intramuscular injections of testosterone enanthate (25-50 mg) may assist in the differential diagnosis of androgen insensitivity, as well as in treatment.

In some mammals, the female exposed to androgens prenatally or in early postnatal life exhibits nontraditional sexual behavior in adult life. Most, but not all, girls who have undergone fetal masculinization from congenital adrenal hyperplasia or from maternal progestin therapy have female sexual identity, although during childhood they may appear to prefer male playmates and activities over female playmates and feminine play with dolls in mothering roles.

In the past it was thought that surgical treatment of ambiguous genitalia to create a female appearance, particularly when a vagina is present, was more successful than construction of male genitalia. Considerable controversy exists regarding these decisions. Sexual functioning is to a large extent more dependent on neurohormonal and behavioral factors than the physical appearance and functional ability of the genitalia. Similarly, controversy exists regarding the timing of the performance of invasive and definitive procedures, such as surgery. Whenever possible without endangering the physical or psychologic health of the child, an expert multidisciplinary team should consider deferring elective surgical repairs and gonadectomies until the child can participate in the informed consent for the procedure. One study (n = 59 boys and 18 girls) with gender dysphoria but without documentation of genomic or enzymologic abnormalities indicated that most of these children no longer have gender dysphoria after completion of puberty. Among those who do, homosexuality and bisexuality are the most frequent diagnoses.

The pediatrician, pediatric endocrinologist, and psychologist, along with the appropriate additional specialists, should provide ongoing compassionate, supportive care to the patient and the patient’s family throughout childhood, adolescence, and adulthood. Support groups are available for families and patients with many of the conditions discussed.