Defect in Cholesterol Synthesis (Smith–Lemli–Opitz Syndrome).

Cholesterol synthesis is required for testosterone and all other hormones that the gonads and adrenal glands produce. The Smith–Lemli–Opitz syndrome, inherited as an autosomal recessive trait, results from an enzymatic defect in the last step of cholesterol metabolism (reduction of 7-dehydrocholesterol due to mutations in the DHCR7 gene).²⁴ These patients variably show ambiguous genitalia with hypospadias, and more constantly a wide range of other somatic abnormalities including a distinctive facial appearance (microcephaly, ptosis, small upturned nose, micrognathia), cleft palate, and limb anomalies (proximally placed thumbs, polydactyly, and 2–3 toe syndactyly).²⁵ Several 46,XY infants with female external genitalia and intra-abdominal testes with epididymides and deferent ducts had a normally shaped uterus and vagina.^26,27 The Y chromosome is normal in these cases, with the affected DHCR7 gene located at 11q13.²⁷

Congenital Lipoid Adrenal Hyperplasia.

Congenital lipoid adrenal hyperplasia (lipoid CAH), the most severe form of CAH, results from mutations in the steroidogenic acute regulatory (STAR) gene as the primary defect (Table 2.2).²⁸ The STAR gene, located on chromosome 8, encodes a protein that helps transport cholesterol into the mitochondria.²⁹ The principal effect is the absence of cholesterol intermediates capable of converting to pregnenolone. Additional damage occurs from the subsequent steroidogenic loss independent of STAR, and results from the effects of the cholesterol esters that accumulate in the adrenal cortex. This leads to cellular damage in the form of salt wasting, hyponatremia, hypovolemia, hyperkalemia, acidosis, and death in infancy. This state of hypergonadotropic hypogonadism shows markedly elevated levels of gonadotropic hormones (LH, follicle-stimulating hormone, ACTH), but markedly impaired synthesis of all gonadal and adrenal cortical steroids, even with trophic stimulation tests.

In the 46,XY male, the external genitalia may be ambiguous to female, but sufficient testosterone must have been secreted during embryogenesis since the internal genitalia are male. Some of these patients may have a palpable gonad in the inguinal canal. These testes disclose immature seminiferous tubules with spermatogonia. Occasional Leydig cells are present. The germ cells may disappear over time, resulting in a Sertoli-only syndrome, although this is not inevitable. Germ cells can persist and rarely develop into intratubular germ cell neoplasia.³⁰

CAH.

Several inherited enzymatic defects, which cause the syndrome of CAH, involve both the synthesis of adrenal mineralocorticoid and glucocorticoid hormones as well as the adrenal and testicular sex hormones. Because of these genetic defects, one or more adrenal cortical enzymes fail to be synthesized or are defective.

The deficiency of 3β-hydroxylase dehydrogenase, like the 20,22-desmolase deficiency, results in decreased synthesis of mineralocorticoid and glucocorticoid hormones as well as adrenal and testicular sex hormones, and may lead to life-threatening salt wasting in infancy. DHEA, a weak androgen secreted in high amounts, results in slight clitoral enlargement in the female, but rarely completely masculinizes the external genitalia in males. Hence, the male may be born with ambiguous genitalia and may resemble a virilized female. Males in whom the defect is partial may be born with hypospadias, but at puberty develop gynecomastia. Over time, the Sertoli cells, which may initially appear normal, undergo atrophy and the spermatogonia change from abundant to rare to absent. The number of Leydig cells may increase with age, but it is unclear whether the hyperplasia is absolute or relative to the atrophy of other elements.³¹

In contrast to the early age of diagnosis in the above two syndromes, the diagnosis in most patients with 17β-hydroxylase deficiency is not suspected until the anticipated time of puberty or later. Occasionally, detailed steroid analysis of the urine of a newborn male presenting with ambiguous genitalia has been performed, indicating that the correct diagnosis can be made in the young.

Deficiency of two enzymes, 17,20-desmolase and 17-hydroxysteroid dehydrogenase (formerly 17-ketosteroid reductase), results in deficient testosterone synthesis but does not affect the production of either mineralocorticoids or glucocorticoids. The former defect (conversion of 17-hydroxypregnenolone to DHEA) is extremely rare. The patients present with ambiguous external genitalia and inguinal or intra-abdominal testes. Spermatogonia were present in the testes of infants but were absent in the biopsies of their older teenage relatives. All had third-degree hypospadias, but normal male internal ductal differentiation.

Genetic males with 17β-hydroxysteroid dehydrogenase (17β-HSD) deficiency have uniformly been raised as females and have unambiguous female external genitalia. Most are diagnosed at or after puberty when they fail to menstruate and instead show signs of virilization such as clitoromegaly (enlarged phallus) and hirsutism.³² Breast development may or may not take place. At surgery, müllerian duct derivatives are absent, consistent with normal AMH action. Wolffian duct differentiation, indicative of testosterone secretion during embryogenesis, is normal.³³ The testes present in the inguinal canal or labia majora contain rare to no spermatogonia, and may exhibit numerous Leydig cells. Detailed endocrine studies have shown that testicular 17β-HSD is under a different genetic control from that in extragonadal tissues, and while affected males lack testicular 17β-HSD, the extragonadal activity is normal or enhanced. More than 15 mutations have been identified in the responsible gene.^11,33

Complete Androgen Receptor Insufficiency (Complete Testicular Feminization).

Complete testicular feminization, the most common form of male pseudohermaphroditism, occurs in 1 : 20,000 newborns. The external genitalia are phenotypically female (Figure 2.6) and, for this reason, the condition is rarely diagnosed before puberty unless an inguinal hernia or labial mass is encountered or unless the disease is known to be familial. Primary amenorrhea is the most common complaint leading to evaluation and subsequent diagnosis. The medical history usually reveals that breast development occurred as expected at puberty, but remains in the pubertal state (Figure 2.7). Pubic and axillary hair is scant (Figure 2.8) and the vagina is shortened. The epididymides are usually cystic and not connected to the testes. The vasa differentia, seminal vesicles, and prostate are absent. As a rule, both the cervix and the uterine corpus are absent. Fallopian tube fragments are found in one-third of cases.⁴⁴ The testes are cryptorchid and may be located in the inguinal canal, the pelvis, or rarely the labia.

In the complete or almost complete form of the syndrome, the individual exhibits a female gender identity with normal extragenital erotogenic sensitivity and normal maternal attitude, emphasizing the need to support the patient as a woman, even with reconstructive surgery.⁴⁵ This condition should be differentiated from defects in steroidogenic factor-1 mutations (XY, sex reversal with androgen insensitivity-like features) with which it can be confused.

The gonads in infants and young children are relatively normal but, by age 5 years, they show abnormalities. By young adulthood, the gonad is often involved with benign or malignant tumors as described later. If tumors are not present by this age, the gonad is usually small and on section is tan to brown and traversed by thin white bands (Figure 2.9). Microscopic examination of the testicular parenchyma discloses immature seminiferous tubules. At earlier ages, the tubules may be clustered in small aggregates (Figure 2.10), but with time they become more sparsely distributed (Figure 2.11). Spermatogonia may be present, but spermatogenesis is absent. The number of spermatogonia found is also age dependent, diminishing as the patient ages. The interstitium, which resembles ovarian stroma, is usually abundant at an early age and over time often becomes more fibrous (Figure 2.12). Fetal-type Leydig cells may be abundant. The Leydig cells in individuals with testicular feminization have an ultrastructure typical of cells involved in active hormone synthesis and the systemic androgen levels in these individuals are typically elevated. These findings indicate that the pathologic defect in the testicular feminization syndrome is an end-organ defect and not lack of hormone production by the testes.

Most testes of affected individuals contain multiple benign nodules that are discrete, firm, yellow to brown, and bulge above the sectioned surface (Figure 2.13). These can be hamartomatous (e.g., Sertoli cell adenoma) or neoplastic (e.g., dysgerminoma or gonadoblastoma like). One finding we have seen characteristically is a 1–2 cm firm white nodule of hyalinized smooth muscle leiomyoma-like tissue that is usually present at one pole of the testis (Figure 2.14). Reactivity for smooth muscle actin confirms its smooth muscle origin (Figure 2.15). Additionally, hamartomatous nodules are present, usually bilaterally, in virtually every case. The typical size varies from 1 mm to 1 cm, but occasionally up to 4 cm.⁴⁴ The bulk of the nodule consists of seminiferous tubules lacking lumina (Figure 2.16). Spermatogonia may be present (Figure 2.17). The seminiferous tubules located outside the nodules have a lamina propria that is of normal thickness in prepubertal testes, but thickened and hyalinized in the adult.⁴⁶ Sertoli cell adenomas, which average 3 cm in diameter, but range to 25 cm (Figure 2.18), are hamartomas composed predominantly or exclusively of closely packed immature seminiferous tubules lacking lumina and lined by immature, uniform Sertoli cells (Figure 2.19), some with germ cells (Figure 2.20).^44,47 The interstitium in the testes of affected patients often resembles ovarian stroma, and frequently contains Leydig cells (Figure 2.10). On rare occasion, Leydig cell nodules form, and have been considered benign tumors (Figure 2.21). Even though tumors have been reported occasionally as malignant, none has shown evidence of invasion or dissemination grossly or microscopically.⁴⁸ In summary, the name applied to each type of nodule is somewhat arbitrary and depends largely upon the types of component present as well as their number and size. Most nodules are classified as hamartomas, Sertoli cell adenomas, or rarely as Leydig cell tumors.

Malignant gonadal tumors develop with increasing frequency with age in patients with testicular feminization. Seminoma is the most commonly encountered gonadal malignancy in this syndrome. Intratubular germ cell neoplasia is sometimes seen, either independently or in association with seminoma (Figures 2.22 and 2.23). Other malignant germ cell tumors and malignant sex cord tumors are also encountered rarely. Unlike mixed gonadal dysgenesis in which tumors develop in young individuals, the risk of malignancy in patients with testicular feminization is only 4% by the age of 25 years, but reaches 33% by 50 years.⁴⁹ Since malignant tumors rarely develop before completion of puberty, castration can usually be delayed until after adolescence, thus permitting the patient to undergo normal pubertal development with spontaneous female secondary sex characteristics.

Partial Androgen Receptor Insufficiency (Incomplete Testicular Feminization).

About 10–50% of patients with the androgen insensitivity syndrome have an incomplete variant.50,51 The clinical manifestations vary depending on the classification system used. If restricted, it resembles complete testicular feminization except that there is partial fusion of the labioscrotal folds and usually some clitoromegaly at birth. If inclusive of all forms of the androgen insensitivity syndrome that are not considered complete testicular feminization, then greater percentages of patients will look and be raised as males.^50,51 Viewed broadly, patients with partial androgen receptor insufficiency form one of the largest groups of intersex patients born with male sex ambiguity.⁴ Like the complete form, underdeveloped wolffian duct derivatives are often present. If the diagnosis is established during childhood, gonadectomy should be performed before puberty, since disfiguring virilization may accompany breast development at puberty. Estrogen therapy should be given at the appropriate time to initiate feminization. The pathologic findings are those described for the complete form of testicular feminization.⁴⁶