Testicular Regression Syndrome

Description

The testicular regression syndrome (TRS) was delineated by Sarto and Opitz (1973), who called it the XY gonadal dysgenesis syndrome. It is characterized primarily by the absence of gonads in an XY person. In most cases, uterus and fallopian tubes are absent but small tubular structures interpreted as mullerian or wolffian rudiments (or both) are present. The range of virilizing effects due to early testicular tissue extends from none in phenotypic females with only slightly hypoplastic normal external genitalia, well-formed but hypoplastic uterus, and well-formed tubes (De Marchi et al., 1981) to the anorchic phenotypic male (Edman et al., 1977). Most affected individuals lack a vagina but a urogenital sinus or pseudovaginal urethral outpouching is found. Partial labioscrotal fusion and clitoris enlargement are common, breast development is absent, and postpubertal eunuchoid habitus is the rule. Sometimes nongenital anomalies are present (summary by Rosenberg et al., 1984).

Clinical Features

Abeyaratne et al. (1969) described 16 cases of apparently complete absence of testes in phenotypic males, including one pair of affected sibs. Ferrier (1969) examined twins, one of whom had anorchia, who were found through blood studies to be probably monozygotic. Familial occurrence was noted by Overzier and Linden (1956).

Bobrow and Gough (1970) also described 2 affected brothers. This familial disorder may be unilateral in a portion of cases. Hall et al. (1975) described anorchia in identical twins and in 2 brothers, and anorchia was unilateral in 3 and bilateral in 1.

Josso and Briard (1980) supported the suggestion that a more appropriate term would be embryonic testicular regression syndrome. They observed two 46,XY sibs with variable degrees of sexual ambiguity. The elder was a phenotypic male with micropenis. The younger, a phenotypic female with slight fusion of the genital folds and absent mullerian ducts, conformed to the usual criteria of true agonadism. Coexistence of anorchia and true agonadism in this sibship suggests that they are fundamentally the same and due to regression of the embryonic testis.

Rosenberg et al. (1984) reported a case of testicular regression in a virilized female and analyzed 20 cases from the literature. They described a 16-year-old 46,XY phenotypic female, born of nonconsanguineous parents and with 3 normal sibs, who had no breast development or pubic hair, slightly hypoplastic female external genitalia with enlarged clitoris and a small pseudovagina. Intravenous urography and urethral cystography showed a hypoplastic masculine urethra. On laparotomy no uterus or gonadal rudiments were observed, although rudiments of wolffian ducts were identified histologically. Basal levels of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) were elevated, consistent with lack of gonadal tissue. Plasma testosterone, dihydrotestosterone, 17-hydroxyprogesterone, and androstenedione were all low; dehydroepiandrosterone (DHEA), predominantly of adrenal origin, was normal. The patient had no other anomalies. Rosenberg et al. (1984) favored autosomal recessive inheritance because of first-cousin parents in 1 instance, agreement with the recessive hypothesis (with sex limitation) on segregation analysis, and familial occurrence in 1 generation only.

De Grouchy et al. (1985) reported a Tunisian sibship of 10 that contained 3 XY sibs with the testicular regression syndrome and severe mental retardation. Since there was an XX sib also with mental retardation, 2 independent disorders may have been segregating in this kindred.

Parisi et al. (2002) described three 46,XY boys, including 2 brothers, with micropenis and poor phallic growth in response to both exogenous human chorionic gonadotropin (HCG) and testosterone therapy in the newborn period. They exhibited low neonatal testosterone levels that failed to respond to HCG stimulation, and had a distinctive gonadotropin profile with reduced LH levels and elevated FSH levels. They had small, cryptorchid testes with subsequent testicular regression and atrophy. In addition, all 3 boys developed microcephaly and mild learning delays. Parisi et al. (2002) noted that the phenotype of these 3 patients was reminiscent of testicular regression syndrome, but stated that patients with testicular regression syndrome have elevation of serum concentrations of both LH and FSH.

Oguz Kutlu et al. (2009) reported a 46,XY boy with testicular regression, born of first-cousin Turkish parents, who presented at 5 months of age with undescended testicles, micropenis, flat scrotum, microcephaly, and psychomotor delay. The patient's LH level was low-normal, and FSH was high. No response was obtained with the HCG stimulation test. Analysis of Sertoli cell function showed levels of inhibin B and anti-Mullerian hormone to be low. At 5 months of age, testicles were visualized bilaterally in the inguinal canals by ultrasound, but by 2 years of age, no testicular tissue was found during inguinal exploration. Oguz Kutlu et al. (2009) stated that the physical findings and laboratory results in this patient were identical to those of the 3 patients studied by Parisi et al. (2002).