Handbook of Clinical Gender Medicine. Группа авторов

7].

      Maternal or Exogenous Sources of Androgens

      Other sources of masculinization with resultant ambiguous genitalia are androgenic stimulation of the fetus in utero from nonfetal sources. Fetal virilization occurs during a critical period between weeks 8 and 13 of gestation and results in labioscrotal fusion and urogenital sinus formation. Female embryos have the same androgen receptor system in the urogenital tract as male embryos; therefore, administration of androgens at the appropriate time during embryogenesis may cause profound masculinization. Internal genitalia are not masculinized and wolffian duct remnants are normal.

      Although CAH is the most common cause of masculinization in the female fetus, masculinization as a consequence of a maternal hormone-producing tumor is becoming a more frequently recognized clinical entity (luteoma of pregnancy, granulosa tumor, arrhenoblastoma, hilar cell tumor, lipoid cell tumor, masculinizing ovarian stromal cell tumor). Other masculinizing tumors which are maternal sources of androgens inducing virilization include: Krukenberg tumor, adrenocortical carcinoma, adrenal myelolipoma, ganglioneuroma, choriocarcinoma, testosterone-secreting adrenal adenoma, and placental site trophoblastic tumor. Bilaterality and multinodularity are more common in luteomas than in these other tumors. Polycystic ovary syndrome and massive ovarian edema are also described as a sporadic cause of virilization during pregnancy.

      Maternal ingestion of androgens, progestagens, and drugs such as danazol, stilboestrol, and 1-9-nortestosterone (for threatened abortion) may cause labial posterior fusion, clitoromegaly, and more pronounced virilization. Ingestion of the off-label ‘appetite stimulant’ cyproheptadine and methandienone (a derivative of testosterone) has been cited as a source of fetal virilization. Maternal application of topical preparations, and exposures noted to induce virilization of the female fetus include: cutaneous androgen preparations, methandrostenolone-containing cream for eczema, and exposure to the fungicide vinclozolin. Only 65% of masculinized mothers deliver masculinized female infants. Protective mechanisms such as active placental aromatization of androgens into estrogens, maternal metabolism of androgens, increases in androgen-binding proteins (SBP and SHBG) under the influence of placental estrogens, and the protective buffering effect of the high concentrations of estrogens found in fetal blood might be responsible for the protection of the fetus against masculinization.

      Undervirilized Males

In 46, XY patients, hypospadiac penis and micropenis are the two main presentations of the undervirilized male. Hypospadias is a result of a development halt of the ventral aspect of the GT during the first term of gestation. A micropenis is a small fully formed GT. Both anomalies are classified as DSD which encompass all congenital genital anomalies and their potential cerebral imprinting. Several epidemiological studies have shown a trend of increased incidence of GT anomalies. Hypospadias incidence is in the vicinity of 1 in 250 male births, with marked variations between countries. The incidence of micropenis is unknown. Causes of hypospadias are essentially unknown and most likely multiple. Four main avenues currently explain faulty development of the GT: (1) genes, gonads, hormonal production, and target tissues; (2) placental hormonal machinery, especially during early gestation; (3) the mother (main biological supervisor), and (4) the maternal environment during gestation [8].

      Genetic Causes

Family cases of hypospadias are well reported, with percentages varying between 10 and 25%. The risk of having another boy with hypospadias in a family with one case is increased 17-fold compared to controls [9]. Many genes have been reported in association with abnormal genital construction: those involved in GT development (HOX, FGF, ATF3, CXorf6, etc.), those involved in gonadal determination and testicular development (WT1, SF1, SOX9, DMRT1, DAX1, WNT4, etc.), those involved in androgen synthesis located in Leydig cells, and those involved in androgen action on target tissues (5-α reductase) [8].

Chromosomal anomalies are found in 7% of patients with isolated hypospadias, more frequently if other genital anomalies are associated. Several well-identified syndromes may associate an abnormal GT: Klinefelter syndrome (47,XXY), mixed gonadal dysgenesis (45, X0/46, XY), 46, XX males with or without a detectable SRY gene, and ovotesticular DSD (46, XX in 60% cases and 46, XY/46, XX in 40%) [10, 11].

      Hormonal Failures

Hormonal failure can be due to insufficient production (gonadal dysgenesis), failed central regulation, or an abnormal response of the target tissue. Evaluation of hormonal secretion varies with the age of the child; on the first day of life, the male newborn plasma androgens are still high due to placental stimulation but will soon fall before the so-called ‘mini puberty’ (days 15-90) where a flare of sexual hormones occurs secondary to gonadotropin stimulation. Beyond the 3rd month of life, androgens are low and will remain so until puberty; AMH and inhibin B (both secreted by the Sertoli cells) are high and represent reliable indicators of Sertoli cells. Leydig cells can be challenged by injections of human chorionic gonadotropin (HCG) or its synthetic recombinant analogs [12]. Plasma AMH above 600 pmol/l is considered a normal value. There is a consensual protocol for HCG stimulation. Failed hormonal gonadal secretions are commonly labeled as ‘gonadal dysgenesis’, although there is no clear histological definition of this entity [13]. Tissue response to androgens can be assessed by clinical changes after hormonal stimulation and by sequencing the genes of the androgen receptors. Beyond these receptors, tissue proteins play an important role in GT construction and can be unbalanced as shown on the ventral aspect of the hypospadiac penis.

      Placental Dysfunction

Low-weight newborns, twins, and very young or ‘old’ mothers represent significant risk factors for abnormal GT. In these circumstances, the placenta may be deficient and may not provide an adequate hormonal climate for the development of the GT. Assessment of placental function is actually mainly represented by the measurement of HCG levels in the mother’s plasma, which is a rough indicator [14].

      The Mother

Given that it is a reference system for biological homeostasis, any disorder of the mother’s hormonal status (hormonal treatment, tumors) may affect the fetus’ hormonal balance and the construction of the GT [15]. Couples with low fertility requiring intracytoplasmic sperm injection or IVF are at risk for the production of a fetus with a higher risk of genital anomalies [16].

      The Environment

Any environmental hormonal disruptors or promoters during pregnancy [17], or even perhaps before, may affect GT development [18, 19]. It is speculated that chemicals such as xenoestrogens (fertilizers, polystyrenes, etc.), estrogen-like molecules, and environmental antiandrogens may have a role in the increasing frequency of these anomalies as well as in the increasing number of undescended testes, testicular cancer, and sperm count deterioration [20,