Male pseudohermaphroditism due to multiple defects in steroid-biosynthetic microsomal mixed-function oxidases. A new variant of congenital adrenal hyperplasia

Age-specific changes in sex steroid biosynthesis and sex development

Normal male sex development requires the SRY gene on the Y chromosome, the regression of Müllerian structures via anti-Müllerian hormone (AMH) signalling, the development of the Wolffian duct system into normal male internal genital structures consequent to testosterone secretion by the testicular Leydig cells, and finally, sufficient activation of testosterone to dihydrotestosterone by 5alpha-reductase. All these events take place during weeks 8-12 of gestation, a narrow window of sexual differentiation. Recent studies in human fetal development have demonstrated the early fetal expression of the adrenocorticotrophic hormone (ACTH) receptor and all steroidogenic components necessary for the biosynthesis of cortisol. These findings provide compelling evidence for the assumed pathogenesis of congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency, diminished feedback to the pituitary due to glucocorticoid deficiency, subsequent ACTH excess, and up-regulation of adrenal androgen production with subsequent virilization. Another CAH variant, P450 oxidoreductase deficiency, manifests with 46,XX disorder of sex development (DSD), i.e., virilized female genitalia, despite concurrently low circulating androgens. This CAH variant illustrates the existence of an alternative pathway toward the biosynthesis of active androgens in humans which is active in human fetal life only. Thus CAH teaches important lessons from nature, providing privileged insights into the window of human sexual differentiation, and particularly highlighting the importance of steroidogenesis in the process of human sexual differentiation.

Differential Inhibition of CYP17A1 and CYP21A2 Activities by the P450 Oxidoreductase Mutant A287P

P450 oxidoreductase (POR) has a pivotal role in facilitating electron transfer from nicotinamide adenine dinucleotide phosphate to microsomal cytochrome P450 (CYP) enzymes, including the steroidogenic enzymes CYP17A1 and CYP21A2. Mutations in POR have been shown recently to cause congenital adrenal hyperplasia with apparent combined CYP17A1 and CYP21A2 deficiency that comprises a variable clinical phenotype, including glucocorticoid deficiency, ambiguous genitalia, and craniofacial malformations. To dissect structure-function relationships potentially explaining this phenotypic diversity, we investigated whether specific POR mutations have differential effects on CYP17A1 and CYP21A2. We compared the impact of missense mutations encoding for single amino acid changes in three distinct regions of the POR molecule: 1), Y181D and H628P close to the central electron transfer area, 2) S244C located within the hinge close to the flavin adenine dinucleotide and flavin mononucleotide domains of POR, and 3) A287P that is clearly distant from the two other regions. Functional analysis using a yeast microsomal assay with coexpression of human CYP17A1 or CYP21A2 with wild-type or mutant human POR revealed equivalent decreases in CYP17A1 and CYP21A2 activities by Y181D, H628P, and S244C. In contrast, A287P had a differential inhibitory effect, with decreased catalytic efficiency (Vmax/Km) for CYP17A1, whereas CYP21A2 retained near normal activity. In vivo analysis of urinary steroid excretion by gas chromatography/mass spectrometry in 11 patients with POR mutations showed that A287P homozygous patients had the highest corticosterone/cortisol metabolite ratios, further indicative of preferential inhibition of CYP17A1. These findings provide novel mechanistic insights into the redox regulation of human steroidogenesis. Differential interaction of POR with electron-accepting CYP enzymes may explain the phenotypic variability in POR deficiency, with additional implications for hepatic drug metabolism by POR-dependant CYP enzymes.

Apparent manifesting heterozygosity in P450 oxidoreductase deficiency and its effect on coexisting 21-hydroxylase deficiency

CONTEXT

P450 oxidoreductase (POR) deficiency is a disorder of steroidogenesis affecting the microsomal P450 enzymes that use POR as an electron donor. The clinical presentation is variable; patients can be asymptomatic or can present with genital anomalies and the Antley-Bixler syndrome, characterized by craniosynostosis and other bony anomalies. Obligately heterozygous parents are normal. Combined POR and 21-hydroxylase deficiencies have not been reported.

OBJECTIVE

The aim was to explore the manifestations of combined deficiencies of 21-hydroxylase and POR and to search for lesions in apparent manifesting POR heterozygotes.

PATIENTS AND METHODS

A newborn female had craniosynostosis, severe salt wasting, minimal virilization, grossly elevated 17OH-progesterone, and minimally elevated androgens. DNA encoding 21-hydroxylase, POR, and fibroblast growth factor receptor 2 was sequenced. For POR, the first untranslated exon (exon 1U), 5' flanking DNA, and most introns were sequenced in five apparent manifesting POR heterozygotes.

RESULTS

CYP21B mutations were found on both alleles, proving classical 21-hydroxylase deficiency. Fibroblast growth factor receptor 2 exons 8 and 10 were normal. A POR mutation, A287P, was found only on the maternal allele. Five previously reported patients had POR mutations found on only one allele, but their clinical characteristics were indistinguishable from patients with mutations on both alleles. Sequencing of exon 1U, 274 bp of POR 5' flanking DNA, and 12 of the 15 POR introns did not identify additional mutations affecting gene expression or splicing.

CONCLUSION

Manifesting heterozygosity is a possible feature of POR deficiency and may ameliorate the findings in coexisting 21-hydroxylase deficiency.

Congenital adrenal hyperplasia and P450 oxidoreductase deficiency

Congenital adrenal hyperplasia (CAH) comprises a group of autosomal recessive disorders, which are usually due to inactivating mutations in single enzymes involved in adrenal steroid biosynthesis. The characteristics of the biochemical and clinical phenotype depend on the specific enzymatic defect. In 21-hydroxylase and 11beta-hydroxylase deficiency only adrenal steroidogenesis is affected, whereas a defect in 3beta-hydroxysteroid dehydrogenase or 17alpha-hydroxylase also involves gonadal steroid biosynthesis. Recently, mutations in the electron donor enzyme P450 oxidoreductase were identified as the cause of CAH with apparent combined 17alpha-hydroxylase and 21-hydroxylase deficiency, thereby illustrating the impact of redox regulation enzymes on steroidogenesis. P450 oxidoreductase deficiency (ORD) has a complex phenotype including two unique features not observed in any other CAH variant, skeletal malformations and severe genital ambiguity in both sexes. Despite invariably low circulating androgens, females with ORD may present with virilized genitalia and mothers may suffer from virilization during pregnancy. This apparently contradictory finding may be explained by the existence of an alternative pathway in human androgen biosynthesis, with important implications for physiology and pathophysiology. This review discusses the biochemical and clinical presentation and the genetic and functional basis of the currently known CAH variants, with a specific focus on ORD.

Linking Antley–Bixler syndrome and congenital adrenal hyperplasia: A novel case of P450 oxidoreductase deficiency

The Antley-Bixler syndrome (ABS) is a multiple congenital malformation syndrome with craniosynostosis, radiohumeral synostosis, femoral bowing, choanal atresia or stenosis, joint contractures, urogenital abnormalities and, often, early death. Autosomal recessive and dominant inheritance have been postulated, as has fluconazole teratogenesis. Mutations in POR (P450 (cytochrome) oxidoreductase, an essential electron donor to enzymes participating in cholesterol biosynthesis), have been identified in some patients with the ABS phenotype. Recent evidence suggests that these mutations cause attenuated steroid hydroxylation, which in turn, causes congenital adrenal hyperplasia (CAH) with ambiguous genitalia in both sexes and glucocorticoid deficiency. Here, we report on a new patient with findings of both ABS and CAH that further illustrates how low maternal estriol at prenatal screening can serve as a marker steroid facilitating early diagnosis.

P450 oxidoreductase deficiency: a new form of congenital adrenal hyperplasia

PURPOSE OF REVIEW

P450 oxidoreductase deficiency--a newly described form of congenital adrenal hyperplasia--typically presents a steroid profile suggesting combined deficiencies of steroid 21-hydroxylase and 17alpha-hydroxylase/17,20-lyase activities. These and other enzymes require electron donation from P450 oxidoreductase. The clinical spectrum of P450 oxidoreductase deficiency ranges from severely affected children with ambiguous genitalia, adrenal insufficiency and the Antley-Bixler skeletal malformation syndrome to mildly affected individuals with polycystic ovary syndrome. We review current knowledge of P450 oxidoreductase deficiency and its broader implications.

RECENT FINDINGS

Since the first report in 2004, at least 21 P450 oxidoreductase mutations have been reported in over 40 patients. The often subtle manifestations of P450 oxidoreductase deficiency suggest it may be relatively common. P450 oxidoreductase deficiency, with or without Antley-Bixler syndrome, is autosomal recessive, whereas Antley-Bixler syndrome without disordered steroidogenesis is caused by autosomal dominant fibroblast growth factor receptor 2 mutations. In-vitro assays of P450 oxidoreductase missense mutations based on P450 oxidoreductase-supported P450c17 activities provide excellent genotype/phenotype correlations. The causal connection between P450 oxidoreductase deficiency and disordered bone formation remains unclear.

SUMMARY

P450 oxidoreductase mutations cause combined partial deficiency of 17alpha-hydroxylase and 21-hydroxylase. Individuals with an Antley-Bixler syndrome-like phenotype presenting with sexual ambiguity or other abnormalities in steroidogenesis should be analyzed for P450 oxidoreductase deficiency.

P450 oxidoreductase deficiency: a new disorder of steroidogenesis

Microsomal P450 enzymes, which metabolize drugs and catalyze steroid biosynthesis require electron donation from NADPH via P450 oxidoreductase (POR). POR knockout mice are embryonically lethal, but we found recessive human POR missense mutations causing disordered steroidogenesis and Antley-Bixler syndrome (ABS), a skeletal malformation syndrome featuring craniosynostosis. Dominant mutations in exons 8 and 10 of fibroblast growth factor receptor 2 (FGFR2) cause phenotypically related craniosynostosis syndromes and were reported in patients with ABS and normal steroidogenesis. Sequencing POR and FGFR2 exons in 32 patients with ABS and/or hormonal findings suggesting POR deficiency showed complete genetic segregation of POR and FGFR2 mutations. Fifteen patients carried POR mutations on both alleles, four carried POR mutations on 1 allele, nine carried FGFR2/3 mutations on one allele and no mutation was found in three patients. The 34 affected POR alleles included 10 with A287P, 7 with R457H, 9 other missense mutations and 7 frameshifts. These 11 missense mutations and 10 others identified by database mining were expressed in E. coli, purified to apparent homogeneity, and their catalytic capacities were measured in four assays: reduction of cytochrome c, oxidation of NADPH, and support of the 17alpha-hydroxylase and 17,20 lyase activities of human P450c17. As assessed by Vmax/Km, 17,20 lyase activity provided the best correlation with clinical findings. Modeling human POR on the X-ray crystal structure of rat POR shows that these mutant activities correlate well with their locations in the structure. POR deficiency is a new disease, distinct from the craniosynostosis syndromes caused by FGFR mutations.

Minireview: regulation of steroidogenesis by electron transfer

Cytochrome P450 enzymes catalyze the degradation of drugs and xenobiotics, but also catalyze a wide variety of biosynthetic processes, including most steps in steroidogenesis. The catalytic rate of a P450 enzyme is determined in large part by the rate of electron transfer from its redox partners. Type I P450 enzymes, found in mitochondria, receive electrons from reduced nicotinamide adenine dinucleotide (NADPH) via the intermediacy of two proteins-ferredoxin reductase (a flavoprotein) and ferredoxin (an iron/sulfur protein). Type I P450 enzymes include the cholesterol side-chain cleavage enzyme (P450scc), the two isozymes of 11-hydroxylase (P450c11beta and P450c11AS), and several vitamin D-metabolizing enzymes. Disorders of these enzymes, but not of the two redox partners, have been described. Type II P450 enzymes, found in the endoplasmic reticulum, receive electrons from NADPH via P450 oxidoreductase (POR), which contains two flavin moieties. Steroidogenic Type II P450 enzymes include 17alpha-hydroxylase/17,20 lyase (P450c17), 21-hydroxylase (P450c21), and aromatase (P450aro). All P450 enzymes catalyze multiple reactions, but P450c17 appears to be unique in that the ratio of its activities is regulated at a posttranslational level. Three factors can increase the degree of 17,20 lyase activity relative to the 17alpha-hydroxylase activity by increasing electron flow from POR: a high molar ratio of POR to P450c17, serine phosphorylation of P450c17, and the presence of cytochrome b(5), acting as an allosteric factor to promote the interaction of POR with P450c17. POR is required for the activity of all 50 human Type II P450 enzymes, and ablation of the Por gene in mice causes embryonic lethality. Nevertheless, mutation of the human POR gene is compatible with life, causing multiple steroidogenic defects and a skeletal dysplasia called Antley-Bixler syndrome.

Diversity and function of mutations in p450 oxidoreductase in patients with Antley-Bixler syndrome and disordered steroidogenesis

P450 oxidoreductase (POR) is the obligatory flavoprotein intermediate that transfers electrons from reduced nicotinamide adenine dinucleotide phosphate (NADPH) to all microsomal cytochrome P450 enzymes. Although mouse Por gene ablation causes embryonic lethality, POR missense mutations cause disordered steroidogenesis, ambiguous genitalia, and Antley-Bixler syndrome (ABS), which has also been attributed to fibroblast growth factor receptor 2 (FGFR2) mutations. We sequenced the POR gene and FGFR2 exons 8 and 10 in 32 individuals with ABS and/or hormonal findings that suggested POR deficiency. POR and FGFR2 mutations segregated completely. Fifteen patients carried POR mutations on both alleles, 4 carried mutations on only one allele, 10 carried FGFR2 or FGFR3 mutations, and 3 patients carried no mutations. The 34 affected POR alleles included 10 with A287P (all from whites) and 7 with R457H (four Japanese, one African, two whites); 17 of the 34 alleles carried 16 "private" mutations, including 9 missense and 7 frameshift mutations. These 11 missense mutations, plus 10 others found in databases or reported elsewhere, were recreated by site-directed mutagenesis and were assessed by four assays: reduction of cytochrome c, oxidation of NADPH, support of 17alpha-hydroxylase activity, and support of 17,20 lyase using human P450c17. Assays that were based on cytochrome c, which is not a physiologic substrate for POR, correlated poorly with clinical phenotype, but assays that were based on POR's support of catalysis by P450c17--the enzyme most closely associated with the hormonal phenotype--provided an excellent genotype/phenotype correlation. Our large survey of patients with ABS shows that individuals with an ABS-like phenotype and normal steroidogenesis have FGFR mutations, whereas those with ambiguous genitalia and disordered steroidogenesis should be recognized as having a distinct new disease: POR deficiency.

Biochemical diagnosis of Antley-Bixler syndrome by steroid analysis

Antley-Bixler syndrome (ABS, MIM 207410) is a skeletal abnormality syndrome primarily affecting head and limbs. Little is known of the origin of the condition but inactivating mutations in the fibroblast growth factor receptor (FGFR2) has been found in some patients. Genital ambiguity is seen occasionally in this condition, suggesting possible disordered steroidogenesis in early pregnancy. We report the steroid excretion of eight patients diagnosed with the syndrome and one with a related condition, a mild phenotype of the disorder since skeletal and genital abnormalities were not evident. The steroid excretion pattern was consistent and very distinctive in all nine patients. Metabolites of the two primary precursors of steroid hormones, pregnenolone and progesterone, were elevated as were the classical diagnostic metabolites for 17- and 21-hydroxylase deficiencies. Cortisol production was typically within the normal range but generally had blunted response to ACTH. Androgen metabolite excretion tends to be low in patients over 2 months of age, but may be elevated in the newborn period. The metabolome suggested attenuated steroid hydroxylation (including 17,20-lyase activity) although underlying cause is yet to be established. Mutations in CYP17 and CYP21 have not been found and currently the prime suspect is an abnormality in an essential redox partner (P450 oxidoreductase). This paper proposes use of the distinctive steroid metabolome as the primary biochemical parameter for diagnosis of ABS, at least the form not associated with FGFR2 mutations.

Disorders of androgen synthesis--from cholesterol to dehydroepiandrosterone

Androgens and estrogens are primarily made from dehydroepiandrosterone (DHEA), which is made from cholesterol via four steps. First, cholesterol enters the mitochondria with the assistance of the steroidogenic acute regulatory protein (StAR). Mutations in the StAR gene cause congenital lipoid adrenal hyperplasia (lipoid CAH), a potentially lethal disease in which virtually no steroids are made. Lipoid CAH is common among Palestinian Arabs and people from eastern Arabia, and among Korean and Japanese people. Second, within the mitochondria, cholesterol is converted to pregnenolone by the cholesterol side chain cleavage enzyme, P450scc; disorder of this enzyme is very rare, probably due to embryonic lethality. Third, pregnenolone undergoes 17alpha-hydroxylation by microsomal P450c17. 17alpha-Hydroxylase deficiency, manifesting as female sexual infantilism and hypertension, is rare except in Brazil. Finally, 17-OH pregnenolone is converted to DHEA by the 17,20 lyase activity of P450c17. The ratio of the 17,20 lyase to 17alpha-hydroxylase activity of P450c17 determines the ratio of C21 to C19 steroids produced. This ratio is regulated posttranslationally by at least three factors: the abundance of the electron-donating protein P450 oxidoreductase (POR), the presence of cytochrome b5 and the serine phosphorylation of P450c17. Mutations of POR are a new, recently described disorder manifesting as the Antley-Bixler skeletal dysplasia syndrome, and a form of polycystic ovary syndrome.

P450 oxidoreductase deficiency: a new disorder of steroidogenesis affecting all microsomal P450 enzymes

Combined partial deficiency of 17alpha-hydroxylase and 21-hydroxylase activities was first described in 1985; however the genes for P450c17 and P450c21 in these patients lack mutations. In 1986 we postulated that this disorder might be due to mutations in P450 oxidoreductase (POR), the flavoprotein that donates electron to these and all other microsomal P450 enzymes, but this hypothesis was not tested until the POR gene sequence became available through the genome database. We found five POR missense mutations in our first four patients. In vitro assays of the activities of these mutations showed that the standard assay of POR activity, reduction of cytochrome c, correlated poorly with the patients' phenotypes, but that assays of POR-supported 17alpha-hydroxylase and 17,20 lyase activities correlated well. POR deficiency is a new disorder of adrenal and gonadal steroidogenesis that affects all microsomal cytochrome P450 enzymes, hence may have important implications for genetic differences in drug metabolism.

A male twin infant with skull deformity and elevated neonatal 17-hydroxyprogesterone: a prismatic case of P450 oxidoreductase deficiency

We report on a male twin infant who presented with brachy-turri-cephaly, frontal bossing, large anterior fontanelle, low set and malformed ears, and mild arachnodactyly. He had normal male genitalia. There was no evidence for maternal virilization during pregnancy. The pattern of malformations resembled Antley-Bixler-Syndrome (ABS). However, sequencing analysis of the fibroblast growth factor receptor 2 gene (FGFR2) did not reveal mutations. The boy's twin sister did not show any somatic or endocrine abnormalities. In the boy, neonatal screening for congenital adrenal hyperplasia was positive with moderately elevated 17-hydroxyprogesterone. Sequence analysis of his CYP21 gene did not reveal any mutations. The short synacthen test revealed an exaggerated 17-hydroxyprogesterone and a blunted cortisol response. Urinary steroid profiling by gas chromatography-mass spectrometry (GC-MS) revealed a unique steroid metabolome suggestive of impaired activity of both 17-hydroxylase and 21-hydroxylase. Clinical and metabolic findings therefore were compatible with the recently described variant of congenital adrenal hyperplasia, P450 oxidoreductase deficiency (ORD). Subsequently, sequencing analysis of CPR, the gene encoding P450 oxidoreductase (OR), revealed a homozygous mutation in the patient, resulting in an amino acid exchange in position 284 of the OR protein (A284P). Both the female twin sister and the parents were heterozygous for the A284P mutation. P450 oxidoreductase deficiency represents a novel autosomal recessively inherited form of congenital adrenal hyperplasia. Its characteristic steroid metabolome can readily be detected by GC-MS analysis of spot urine. Clinical features may include an ABS phenotype, ambiguous genitalia (virilization in girls, feminization in boys), and glucocorticoid deficiency. If required, hydrocortisone replacement should be provided.

Abnormal steroidogenesis in three patients with Antley-Bixler syndrome: apparent decreased activity of 17alpha-hydroxylase, 17,20-lyase and 21-hydroxylase

BACKGROUND

Antley-Bixler syndrome (ABS) is characterized mainly by abnormal skeletal morphogenesis such as craniosynostosis and radiohumeral synostosis, and by ambiguous genitalia in some cases. The mechanisms resulting in these deformities have not been determined.

METHODS

The adrenal and gonadal function of three Japanese ABS patients were evaluated. Patient 1 (17-year-old-male) had bilateral cryptoorchidism, delayed puberty and symptoms of glucocorticoid deficiency. Patient 2 (14-year-old male) and patient 3 (4-year-old female) presented with emaciation. Additionally, patient 3 had partial labial fusion and common urogenital sinus. In each patient, blood sampling for steroid analysis before and after rapid adrenocorticotropic hormone (ACTH) stimulation was carried out. Additionally, urinary steroids were quantified. Molecular analysis of CYP17 and CYP21A2 were also performed.

RESULTS

All patients showed elevated basal 17alpha-deoxysteroid levels. Although the 17alpha-deoxysteroid levels further increased after rapid ACTH stimulation, 17alpha-hydroxysteroids including cortisol did not respond, suggesting impaired 17alpha-hydroxylation. Patient 1 and patient 2 showed low adrenal androgen blood levels both before and after rapid ACTH stimulation. Patient 3 showed lower than normal excretions of urinary androgens. Additionally, a prolonged ACTH stimulation in patient 3 failed to elicit significant increase of adrenal androgens. These findings suggested impaired 17,20-lyase activity. In contrast to attenuated 17alpha-hydroxycorticosteroids, notably cortisol, elevated 17alpha-hydroxyprogesterone (17OHP) levels were observed, not only in pubertal patients (1 and 2) but also in prepubertal patient 3, indicating impaired 21-hydroxylation. This assumption was supported by increased urinary 21-deoxycortisol metabolite excretion in patients 2 and 3. With the exception of a heterozygous mutation of CYP17 in one of the patients, other mutations of this gene or CYP21A2 were identified in any of the patients.

CONCLUSION

Combined decreased 17alpha-hydroxylation, 17,20-lyase activity and 21-hydroxylation was detected in three ABS patients. Considering that the enzymes responsible are all cytochrome P450 enzymes and that another cytochrome P450 enzyme, lanosterol 14alpha-demethylase, has recently been shown to be impaired in an ABS patient, we speculate that dysfunction of a system which commonly regulates cytochrome P 450 activity may be responsible for the ABS phenotype.

P450 oxidoreductase deficiency: a new disorder of steroidogenesis with multiple clinical manifestations

Combined partial deficiency of 17alpha-hydroxylase and 21-hydroxylase is well-described, but patients' genes for these enzymes lack mutations. Recent work has identified mutations in the gene for P450 oxidoreductase (POR) in such patients. POR-deficient individuals have a broad range of disorders, from infants with congenital malformations to women with the polycysic ovary syndrome. POR transfers electrons to all microsomal P450 enzymes: its deficiency affects steroidogenesis, drug metabolism and other processes.

Congenital adrenal hyperplasia caused by mutant P450 oxidoreductase and human androgen synthesis: analytical study

BACKGROUND

Congenital adrenal hyperplasia with apparent combined P450C17 and P450C21 deficiency is associated with accumulation of steroid metabolites, indicating impaired activity of 17alpha-hydroxylase and 21-hydroxylase. However, no mutations have been reported in the CYP17 and CYP21 genes, which encode these P450 enzymes. Affected girls are born with ambiguous genitalia, but their circulating androgens are low, and virilisation does not progress. We aimed to investigate the underlying molecular basis of congenital adrenal hyperplasia with apparent combined P450C17 and P450C21 deficiency in affected children.

METHODS

We did sequence analysis of the human gene encoding P450 oxidoreductase, an enzyme that is important in electron transfer from NADPH to P450C17 and P450C21. We studied two unrelated families with a total of three affected children and 100 healthy controls. Wild-type and mutant P450 oxidoreductase proteins were bacterially expressed, purified, and assayed for cytochrome c reductase activity.

FINDINGS

We identified four mutations encoding single aminoacid changes in P450 oxidoreductase. All patients were compound heterozygotes, whereas their parents and an unaffected sibling harboured a mutation in only one allele. By contrast, no mutations were noted in the controls. Bacterial expression of recombinant mutant proteins revealed deficient or reduced enzyme activity.

INTERPRETATION

Molecular pathogenesis of this form of congenital adrenal hyperplasia is caused by mutations in the gene encoding P450 oxidoreductase. Deficiency of this enzyme could suggest an alternative pathway in human androgen synthesis, present only in fetal life, which explains the combination of antenatal androgen excess and postnatal androgen deficiency.

Mutant P450 oxidoreductase causes disordered steroidogenesis with and without Antley-Bixler syndrome

Deficient activities of multiple steroidogenic enzymes have been reported without and with Antley-Bixler syndrome (ABS), but mutations of corresponding cytochrome P450 enzymes have not been found. We identified mutations in POR, encoding P450 oxidoreductase, the obligate electron donor for these enzymes, in a woman with amenorrhea and three children with ABS, even though knock-out of POR is embryonically lethal in mice. Mutations of POR also affect drug-metabolizing P450 enzymes, explaining the association of ABS with maternal fluconazole ingestion.

Mutations in CYP11B1 gene: phenotype-genotype correlations

11beta-hydroxylase deficiency, an autosomal recessive disorder, is the second most common cause of congenital adrenal hyperplasia. We studied four subjects with classic 11beta-hydroxylase deficiency and severe hypertension: a 46,XX affected subject from a Turkish family with severe ambiguity of the external genitalia and hypertension, and three affected 46,XY subjects from a Dominican kindred with isosexual precocious puberty and severe hypertension. The affected subjects had significantly elevated plasma 11-desoxycortisol, 11-desoxycorticosterone, Delta4-androstenedione, and testosterone. To determine the molecular genetic defects, genomic DNA was isolated from the leukocytes of affected subjects and their family members. The encoding region of the 11beta-hydroxylase gene (CYP11B1) was amplified by PCR with specific primers. Using single-stranded DNA conformational polymorphism (SSCP) and DNA sequencing, a nonsense mutation in exon 6 of CYP11B1 in the affected 46,XX subject from the Turkish family was identified, where a cytosine was substituted by a thymidine, resulting in the replacement of glutamine (CAG) by a stop codon (TAG) at amino acid position 338 (Q338X). In the three 46,XY Dominican boys, the mutation was also a nonsense mutation in exon 6 of CYP11B1, where a cytosine was substituted by a thymidine, resulting in the replacement of glutamine (CAG) by a stop codon (TAG) at amino acid position 356 (Q356X). Both mutations result in the biosynthesis of a truncated 11beta-hydroxylase protein with loss of enzymatic activity. Heterozygosity was determined in family members of both probands including parents and siblings. These results indicate that mutations of CYP11B1 in these subjects are responsible for their clinical syndromes.

The genetics, pathophysiology, and management of human deficiencies of P450c17

P450c17 commands a central role in human steroidogenesis as the qualitative regulator of steroid hormone flux. Consequently, the study of P450c17 deficiencies in human beings serves to illustrate many aspects of the physiology of steroid biosynthesis and to demonstrate salient features of the genetics and biochemistry of P450c17 itself. Furthermore, classic 17-hydroxylase deficiency was first described in patients with sexual infantilism and hypertension, but it is now recognized that partial and selective forms of P450c17 deficiencies also exist. These patients demonstrate a range of phenotypes, illustrating the multiple roles of P450c17 in human biology. This article reviews the genetics and biochemistry of P450c17 as a prelude for understanding the pathophysiology of these diseases and approaches to their diagnosis and management.

Menstrual disturbance and hypersecretion of progesterone in women with congenital adrenal hyperplasia due to 21-hydroxylase deficiency

OBJECTIVE

While menstrual disturbance is often quoted as a feature of congenital adrenal hyperplasia (CAH), little is known about the mechanism of this symptom. We set out to determine the relationship between menstrual pattern and biochemical characteristics of women with CAH due to 21-hydroxylase deficiency.

PATIENTS AND DESIGN

All 21 female patients with classic CAH attending the adult endocrinology clinics at The Middlesex Hospital were reviewed. Their ages at menarche and menstrual pattern were recorded and blood samples were taken in the follicular phase of the menstrual cycle when on their usual maintenance therapy.

MEASUREMENTS

Measurements of serum LH, FSH, progesterone, 17 alpha-hydroxyprogesterone, testosterone, androstenedione and plasma renin activity were recorded. Urinary steroid profiles were obtained by gas chromatography and mass spectrometry. Molecular genetic analysis of the 21-hydroxylase gene was performed on leucocyte DNA.

RESULTS

In the 18 patients who had spontaneous menarche the degree of menstrual disturbance and progesterone excess was related to the effectiveness of adrenal suppressive therapy. Three out of 21 patients, however, failed to experience menarche on standard medical therapy. These patients with primary amenorrhoea were characterized by reduced endometrial thickening, by non-suppressible serum progesterone concentrations despite suppression of 17 alpha-hydroxyprogesterone levels and by the presence of progesterone metabolites in urinary steroid profiles. Molecular genetic analysis did not differentiate between patients with raised progesterone concentrations and those without.

CONCLUSION

A subgroup of women with congenital adrenal hyperplasia have the triad of non-suppressible serum progesterone of adrenal origin, primary amenorrhoea and infertility due to failure of endometrial thickening. The characteristic urinary steroid profile best distinguishes this subgroup of women from others with congenital adrenal hyperplasia and menstrual disturbance due to inadequate adrenal suppression.

Ambiguous genitalia due to partial activity of cytochromes P450c17 and P450c21

We describe a patient with male pseudohermaphrodism who has normal basal serum concentrations of cortisol and high basal levels of progesterone and 17 hydroxyprogesterone. Serum concentrations of androstendione, dehydroepiandrosterone sulfate and testosterone were low. On adequate human chorionic gonadotropin (HCG) stimulation, no rise in serum androstendione, dehydroepiandrosterone sulfate or testosterone concentrations was observed. After ACTH stimulation there was an excessive rise in progesterone and 17 hydroxyprogesterone with no rise in androstendione, dehydroepiandrosterone sulfate, testosterone, deoxycorticosterone or cortisol. These clinical and laboratory data suggest that the patient has a combined defect in both cytochromes P450c17 and P450c21. The genes coding for these cytochromes are on different chromosomes, 10 and 6, respectively. Unlike isolated 21 hydroxylase deficiency where all identical HLA siblings suffer from the disease, HLA typing of the patient's family revealed a healthy brother with identical HLA. This suggests that the gene coding for P450c21 on chromosome 6 is not affected and that the lesion might be on a common enzyme which donates an electron to both cytochromes, most probably a flavoprotein.

Partial 17, 20-desmolase and 17 alpha-hydroxylase deficiencies in a 16-year-old boy

Thirteen plasma steroids as well as ACTH, LH and FSH were measured by specific RIAs under basal and dynamic conditions in a 16-year-old boy (normal external genitalia, 46, XY karyotype) who presented slowness and unachievement of pubertal development. On the delta 4-pathway: basal levels of testosterone and dihydrotestosterone were low- with a normal ratio-, delta 4-androstenedione and 11 beta-hydroxyandrostenedione were in the low normal range. Meanwhile, 17 alpha-hydroxyprogesterone and progesterone levels were markedly elevated. On the delta 5-pathway: dehydroepiandrosterone was extremely low while 17 alpha-hydroxypregnenolone and pregnenolone were almost normal; dehydroepiandrosterone sulfate was subnormal while pregnenolone sulfate was normal. Cortisol, aldosterone were normal while ACTH was moderately increased. Basal and responsive levels of LH and FSH were markedly increased. ACTH stimulation induced a subnormal rise of cortisol and 11 beta-hydroxyandrostenedione, a low or absent rise of dehydroepiandrosterone, 17 alpha-hydroxypregnenolone, androstenedione and 17 alpha-hydroxyprogesterone contrasting with a marked rise of pregnenolone and progesterone. After hCG stimulation, responses were low for testosterone, extremely high for 17 alpha-hydroxyprogesterone with a normalisation of the 17 alpha-hydroxyprogesterone/progesterone ratio. Fluoxymesterone dramatically reduced the pathologically high basal levels of progesterone and 17 alpha hydroxyprogesterone. Dexamethasone induced only a minute decrease in the delta 4-progestagens, a marked decrease in pregnenolone, with a more than 80% reduction of 17 alpha- hydroxypregnenolone, dehydroepiandrosterone, dehydroepiandrosterone sulfate and androstenedione. These data suggest a defect involving the cytochrome P450 common to both 17 alpha-hydroxylase and 17, 20-desmolase activities.(ABSTRACT TRUNCATED AT 250 WORDS)

Abnormal sexual differentiation and neoplasia

The prevalence of neoplasia is increased in individuals with certain disorders of sexual differentiation. Etiology and frequency of neoplasia vary with the particular disorder. In uncomplicated cryptorchidism, the testis is at least 10 times more likely to undergo neoplastic transformation than a normal scrotal testis. Neoplasia probably is a function of both testicular location (intraabdominal) and underlying dysgenetic structure. If cryptorchidism is unilateral, and if orchiopexy has not been performed prior to age 6-10 years, orchiectomy should be encouraged. In those forms of gonadal dysgenesis not associated with a Y chromosome (e.g., 45,X; 45,X/46,XX; 46,XX) there is no definite increase in neoplasia, suggesting that elevated gonadotropin levels per se are not carcinogenic. Gonadal tumors are found in at least 30% of individuals with XY gonadal dysgenesis and are particularly frequent (55%) in H-Y antigen-positive patients. These tumors are almost always gonadoblastomas or dysgerminomas. Similar tumors are found in 15%-20% of 45,X/46,XY individuals. In either situation the neoplastic transformation could be a) secondary to the existence of XY gonadal tissue in an inhospitable environment, or b) integrally related to that process--genetic or cytogenetic--producing the dysgenetic gonads. The risk of neoplasia is sufficiently high that most of these patients should be offered early gonadal extirpation. The prevalence of gonadal tumors is not increased in Klinefelter's syndrome, further indicating that gonadotropins are not carcinogenic per se. However, Klinefelter patients are 20 times more likely to develop a carcinoma of the breast than are 46,XY males. Extragonadal germ cell tumors also are more common. In female pseudohermaphrodites there is probably no increased risk of neoplasia, whereas, in true hermaphrodites neoplasia is unusual but does occur. Neoplasia occurs in patients with complete testicular feminization (complete androgen insensitivity) but rarely in those with incomplete testicular feminization/Reifenstein's syndrome, 5 alpha-reductase deficiency, anorchia, agonadia, or testosterone biosynthetic defects. In complete testicular feminization the risk of malignant tumors is small prior to age 25. After age 25, it is about 2%-5%. Orchiectomy is recommended after pubertal feminization.

The prevalence of 5 alpha-reductase deficiency in children with ambiguous genitalia in the Dominican Republic

During a 10-year period 65 children and adolescents with ambiguous genitalia from the Dominican Republic, not known through kindred studies of 5 alpha-reductase deficiency, were evaluated. Plasma androgen determinations were performed before and/or after Leydig cell stimulation of the testes with human chorionic gonadotropin. Of the children there were 24 female pseudohermaphrodites, 21 of whom had 21-hydroxylase deficiency, 1 true hermaphrodite and 40 (62 per cent) male pseudohermaphrodites. One child had a human chorionic gonadotropin response suggestive of 17-20 desmolase deficiency, and on further evaluation he also had partial deficiencies of the enzymes 21-hydroxylase and 17 alpha-hydroxylase. Five subjects had a female phenotype and subnormal androgen responses to human chorionic gonadotropin. In 5 of 33 male pseudohermaphrodites with a normal testosterone response to human chorionic gonadotropin 5 alpha-reductase deficiency was suspected by elevated plasma testosterone/dihydrotestosterone ratios before and/or after human chorionic gonadotropin stimulation. The diagnosis of 5 alpha-reductase deficiency was confirmed by elevated 5 beta/5 alpha urinary C19 and C21 steroid metabolite ratios. One subject with 5 alpha-reductase deficiency was traced to the original Dominican kindred of 38 affected subjects. Pedigree analysis of another proband revealed 3 additional affected relatives. Four subjects with a normal testosterone response to human chorionic gonadotropin had XO/XY gonadal dysgenesis. There were 25 male pseudohermaphrodites with normal plasma testosterone and dihydrotestosterone responses to human chorionic gonadotropin, who were not diagnosed by this methodology. This study reveals that 5 alpha-reductase deficiency occurs with a frequency of 13 per cent as a cause of male pseudohermaphroditism in the Dominican Republic with approximately the same frequency as XO/XY gonadal dysgenesis. Unlike female pseudohermaphrodites, the majority of male subjects with pseudohermaphroditism remain unclassified by these techniques.

Profiling steroid hormones and urinary steroids

This paper reviews techniques utilized in the profiling of steroids in body fluids and tissues. Methods for profiling plasma unconjugated steroids and urinary steroid metabolites are focused on. Concentrations or levels of excretion of a variety of steroids have been documented and reviewed. The importance of profiling techniques in the study of normal and pathophysiology of hormonal steroids is discussed.