※ 引述《Pardice (一直走下去)》之铭言： : 54 下列对於5α-reductase deficiency的叙述，何者错误？ : (A)这些女性患者的基因型为XY型 : (B)这些女性患者的乳房发育相当於正常女性 : (C)这些女性患者可能会有睾丸存在 : (D)这些女性患者体内无法使testosterone转换为dihydrotestosterone : 网路上找到的资料 : 　 　 : 　 这类病人染色体是正常的男性(46,XY)，有分化良好的睾丸，正常的男性内生殖器，没 : 有子宫及输卵管的存在，但是外生殖器确是不明确的。通常出生时，阴茎很小，像阴蒂一 : 样；睾丸的位置在腹股沟或所谓的阴囊中。由於第二性徵的发育主要是雄性激素的作用， : 因此到了青春期会有明显的男性化，但不会出现男性女乳( Gynecomastia )。 : 申覆理由: 根据定义，有Y就是男人。此类病人根本不是女人， : 每个选项叙述都有错，建议送分。 : 同意请"附议" : 不知道有没有强者可以神到Novak... : 目前学校图书馆的Novak被借走，...苦无有力资料佐证 Nelson Textbook of Pediatrics, 18th ed. Chapter 589 – Disorders of Sex Development (Intersex) DEFECTS IN ANDROGEN ACTION 5α-REDUCTASE DEFICIENCY. Decreased production of dihydrotestosterone (DHT) in utero results in severe ambiguity of the external genitals of the affected male fetus. 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. 589-3). Testes are in the inguinal canals or labioscrotal folds and are normal histologically. There are no mu"llerian 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. Click to view full size figure Figure 589-3 5α-Reductase deficiency. (From Wales JKH, Wit JM, Rogol AD: Pediatric Endocrinology and Growth, 2nd edition. Philadelphia, Elsevier/Saunders, 2003, p 165.) The adult height reached is close to that of the father and other male siblings. There is, however, significant phenotypic heterogeneity. This has led to a classification of such patients into 5 types of steroid 5α -reductase deficiency (SRD) ranging from complete female (type 5), to partial female (type 4), ambiguous (type 3), predominantly male with micropenis (type 2), and completely male phenotype without apparent undervirilization (type 1). 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 correlation between severity of the genetic defect 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 should be distinguished from androgen insensitivity syndrome. The biochemical diagnosis 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 and 5α to 5α metabolites. 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. Most but, importantly, not all children 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 contribute 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. 这autosomal recessive疾病只限男性胎儿，所以不可能会有女性患者 题意错误，建议送分 虽然这科不是考小儿科，但性别分化的议题还是小儿科专长领域吧 附上小儿科Bible，应该还够力 -- --

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