Gene conversions and rearrangements cause discordance between inheritance of forms of 21-hydroxylase deficiency and HLA types

Assessment of the most common CYP21A2 point mutations in a cohort of congenital adrenal hyperplasia patients from Egypt

Objectives Congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency (21-OHD) is a common autosomal recessive disorder caused by defects in the CYP21A2 gene. We aimed to determine the prevalence of the most commonly reported mutations among 21-OHD Egyptian patients and correlate genotype with phenotype. Methods Molecular analysis of the CYP21A2 gene was performed for the detection of the six most common point mutations (p.P30L, p.I172N, p.V281L, p.Q318X, the splice site mutation Int2 [IVS2-13A/C>G], and the cluster of three mutations [p.I236N, p.V237E, and p.M239K] designed as CL6). Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method was performed on 47 unrelated Egyptian 21α-OH deficiency patients and their available parents to detect the presence of the six most common point mutations. Results Screening for the six most common point mutations in CYP21A2 gene, revealed mutations in 87.2% (82/94) of the studied alleles corresponding to 47 Egyptian patients. The most common mutation among the studied cases was IVS2-13C/A>G that was found to be presented in a frequency of 46.8% (44/94). The genotype/phenotype correlations related to null, A, and B groups were with PPV of 100, 55.5, and 83.3%, respectively. Conclusions The described method diagnosed CAH in 80.8% of the studied patients. Good correlation between genotype and phenotype in salt wasting and simple virilizing forms is determined, whereas little concordance is seen in nonclassical one. Furthermore, studying the carrier frequency of 21-OHD among the normal population is of great importance.

Abiraterone acetate to lower androgens in women with classic 21-hydroxylase deficiency

CONTEXT

Chronic supraphysiological glucocorticoid therapy controls the androgen excess of 21-hydroxylase deficiency (21OHD) but contributes to the high prevalence of obesity, glucose intolerance, and reduced bone mass in these patients. Abiraterone acetate (AA) is a prodrug for abiraterone, a potent CYP17A1 inhibitor used to suppress androgens in the treatment of prostate cancer.

OBJECTIVE

The objective of the study was to test the hypothesis that AA added to physiological hydrocortisone and 9α-fludrocortisone acetate corrects androgen excess in women with 21OHD without causing hypertension or hypokalemia.

DESIGN

This was a phase 1 dose-escalation study.

SETTING

The study was conducted at university clinical research centers.

PARTICIPANTS

We screened 14 women with classic 21OHD taking hydrocortisone 12.5-20 mg/d to enroll six participants with serum androstenedione greater than 345 ng/dL (>12 nmol/L).

INTERVENTION

AA was administered for 6 days at 100 or 250 mg every morning with 20 mg/d hydrocortisone and 9α-fludrocortisone acetate.

MAIN OUTCOME MEASURE

The primary endpoint was normalization of mean predose androstenedione on days 6 and 7 (< 230 ng/dL [<8 nmol/L)] in greater than 80% of participants. Secondary end points included serum 17-hydroxyprogesterone and testosterone (T), electrolytes, plasma renin activity, and urine androsterone and etiocholanolone glucuronides.

RESULTS

With 100 mg/d AA, mean predose androstenedione fell from 764 to 254 ng/dL (26.7-8.9 nmol/L). At 250 mg/d AA, mean androstenedione normalized in five participants (83%) and decreased from 664 to 126 ng/dL (23.2-4.4 nmol/L), meeting the primary end point. Mean androstenedione declined further during day 6 to 66 and 38 ng/dL (2.3 and 1.3 nmol/L) at 100 and 250 mg/d, respectively. Serum T and urinary metabolites declined similarly. Abiraterone exposure was strongly negatively correlated with mean androstenedione. Hypertension and hypokalemia were not observed.

CONCLUSION

AA 100-250 mg/d added to replacement hydrocortisone normalized several measures of androgen excess in women with classic 21OHD and elevated serum androstenedione.

The ribosomal basis of Diamond-Blackfan Anemia: mutation and database update

Diamond-Blackfan Anemia (DBA) is characterized by a defect of erythroid progenitors and, clinically, by anemia and malformations. DBA exhibits an autosomal dominant pattern of inheritance with incomplete penetrance. Currently nine genes, all encoding ribosomal proteins (RP), have been found mutated in approximately 50% of patients. Experimental evidence supports the hypothesis that DBA is primarily the result of defective ribosome synthesis. By means of a large collaboration among six centers, we report here a mutation update that includes nine genes and 220 distinct mutations, 56 of which are new. The DBA Mutation Database now includes data from 355 patients. Of those where inheritance has been examined, 125 patients carry a de novo mutation and 72 an inherited mutation. Mutagenesis may be ascribed to slippage in 65.5% of indels, whereas CpG dinucleotides are involved in 23% of transitions. Using bioinformatic tools we show that gene conversion mechanism is not common in RP genes mutagenesis, notwithstanding the abundance of RP pseudogenes. Genotype-phenotype analysis reveals that malformations are more frequently associated with mutations in RPL5 and RPL11 than in the other genes. All currently reported DBA mutations together with their functional and clinical data are included in the DBA Mutation Database.

The molecular biology, biochemistry, and physiology of human steroidogenesis and its disorders

Steroidogenesis entails processes by which cholesterol is converted to biologically active steroid hormones. Whereas most endocrine texts discuss adrenal, ovarian, testicular, placental, and other steroidogenic processes in a gland-specific fashion, steroidogenesis is better understood as a single process that is repeated in each gland with cell-type-specific variations on a single theme. Thus, understanding steroidogenesis is rooted in an understanding of the biochemistry of the various steroidogenic enzymes and cofactors and the genes that encode them. The first and rate-limiting step in steroidogenesis is the conversion of cholesterol to pregnenolone by a single enzyme, P450scc (CYP11A1), but this enzymatically complex step is subject to multiple regulatory mechanisms, yielding finely tuned quantitative regulation. Qualitative regulation determining the type of steroid to be produced is mediated by many enzymes and cofactors. Steroidogenic enzymes fall into two groups: cytochrome P450 enzymes and hydroxysteroid dehydrogenases. A cytochrome P450 may be either type 1 (in mitochondria) or type 2 (in endoplasmic reticulum), and a hydroxysteroid dehydrogenase may belong to either the aldo-keto reductase or short-chain dehydrogenase/reductase families. The activities of these enzymes are modulated by posttranslational modifications and by cofactors, especially electron-donating redox partners. The elucidation of the precise roles of these various enzymes and cofactors has been greatly facilitated by identifying the genetic bases of rare disorders of steroidogenesis. Some enzymes not principally involved in steroidogenesis may also catalyze extraglandular steroidogenesis, modulating the phenotype expected to result from some mutations. Understanding steroidogenesis is of fundamental importance to understanding disorders of sexual differentiation, reproduction, fertility, hypertension, obesity, and physiological homeostasis.

Novel deletion alleles carrying CYP21A1P/A2 chimeric genes in Brazilian patients with 21-hydroxylase deficiency

BACKGROUND

Congenital adrenal hyperplasia due to 21-hydroxylase deficiency is caused by deletions, large gene conversions or mutations in CYP21A2 gene. The human gene is located at 6p21.3 within a locus containing the genes for putative serine/threonine Kinase RP, complement C4, steroid 21-hydroxylase CYP21 tenascin TNX, normally, in a duplicated cluster known as RCCX module. The CYP21 extra copy is a pseudogene (CYP21A1P). In Brazil, 30-kb deletion forming monomodular alleles that carry chimeric CYP21A1P/A2 genes corresponds to ~9% of disease-causing alleles. Such alleles are considered to result from unequal crossovers within the bimodular C4/CYP21 locus. Depending on the localization of recombination breakpoint, different alleles can be generated conferring the locus high degree of allelic variability. The purpose of the study was to investigate the variability of deleted alleles in patients with 21-hydroxylase deficiency.

METHODS

We used different techniques to investigate the variability of 30-kb deletion alleles in patients with 21-hydroxylase deficiency. Alleles were first selected after Southern blotting. The composition of CYP21A1P/A2 chimeric genes was investigated by ASO-PCR and MLPA analyses followed by sequencing to refine the location of recombination breakpoints. Twenty patients carrying at least one allele with C4/CYP21 30-kb deletion were included in the study.

RESULTS

An allele carrying a CYP21A1P/A2 chimeric gene was found unusually associated to a C4B/C4A Taq I 6.4-kb fragment, generally associated to C4B and CYP21A1P deletions. A novel haplotype bearing both p.P34L and p.H62L, novel and rare mutations, respectively, was identified in exon 1, however p.P30L, the most frequent pseudogene-derived mutation in this exon, was absent. Four unrelated patients showed this haplotype. Absence of p.P34L in CYP21A1P of normal controls indicated that it is not derived from pseudogene. In addition, the combination of different approaches revealed nine haplotypes for deleted 21-hydroxylase deficiency alleles.

CONCLUSIONS

This study demonstrated high allelic variability for 30-kb deletion in patients with 21-hydroxylase deficiency indicating that a founder effect might be improbable for most monomodular alleles carrying CYP21A1P/A2 chimeric genes in Brazil.

p.H62L, a rare mutation of the CYP21 gene identified in two forms of 21-hydroxylase deficiency

CONTEXT

Steroid 21-hydroxylase deficiency is the most common enzymatic defect causing congenital adrenal hyperplasia with good genotype/phenotype relationships for common mutations. To determine the severity of rare mutations is essential for genetic counseling and better understanding of the structure-function of the cytochrome P450c21.

OBJECTIVE

The p.H62L mutation was the most frequent of 60 new mutations detected in 2900 steroid 21-hydroxylase deficiency patients, either isolated or associated on the same allele with a mild mutation (p.P453S, p.P30L, or partial promoter). Because phenotypes seemed to differ between patients with isolated or associated p.H62L, a detailed phenotype description and functional studies were performed.

RESULTS

Regarding phenotype, patients with isolated p.H62L had a nonclassical form, whereas patients with the association p.H62L + mild mutation had a simple virilizing form. Functional studies showed that p.H62L reduced the conversion of the two substrates, progesterone and 17-hydroxyprogesterone, in the same way as the mild p.P453S; the association p.H62L + p.P453S decreased enzymatic activity more strongly while conserving residual activity at a level intermediate between p.P453S and p.I172N. This suggested that p.H62L was a mild mutation, whereas a synergistic effect occurred when it was associated. Analysis of p.H62L in a three-dimensional model structure of the CYP21 protein explained the observed in vitro effects, the H62 being located in a domain implied in membrane anchoring.

CONCLUSION

According to phenotype and functional studies, p.H62L is a mild mutation, responsible for a more severe phenotype when associated with another mild mutation. These data are important for patient management and genetic counseling.

Prevalence of nonclassic adrenal hyperplasia (NCAH) in hyperandrogenic women

OBJECTIVE

The clinical symptoms of nonclassic adrenal hyperplasia (NCAH) are identical with polycystic ovary syndrome (PCOS). The aim of our study was to determine the prevalence of nonclassic adrenal hyperplasia (21-hydroxylase-deficiency) in hyperandrogenic women, its biochemical, endocrine and clinical characteristics and to compare them with parameters of patients with ovarian hyperandrogenism.

METHODS

Since 1999, 298 patients with elevation of at least one androgen and manifestation of one of the clinical androgenic symptoms (oligo/amenorrhea, hirsutism or acne) have been identified in our database. A diagnosis of NCAH was considered when the basal or stimulated 17-hydroxyprogesterone was elevated.

RESULTS

Only eight patients were identified as having 21- hydroxylase deficient NCAH in the whole group of 298 hyperandrogenic women. Hirsutism and acne were found only in three, two patients, five of them had oligo/amenorrhea. Seven patients had both elevated basal and stimulated 17-hydroxyprogesterone, while in one case only elevation of stimulated level was found. All of the NCAH patients had elevated concentrations of testosterone, six DHEA, lower SHBG was found in four patients. Surprisingly, none of the NCAH patients had increased DHEAS.

CONCLUSION

In our study, the prevalence of NCAH in hyperandrogenic women was 2.68%. Their leading symptom was oligomenorrhea, skin androgenic disorders were a minor clinical problem. None of the NCAH patients had an elevated DHEAS, the androgen dominantly produced by the adrenal glands.

Basic concepts and recent developments in human steroid hormone biosynthesis

The biosynthesis of steroid hormones requires the coordinated expression of the enzymes that comprise the pathways via which specific hormones are synthesized. These pathways and their associated enzymes are typically subject to regulation consisting of trophic hormone stimuli and feedback mechanisms. Very few tissues contribute substantially to de novo steroidogenesis, primarily the adrenal glands, the gonads, and the placenta. Both the embryonic origins and the signaling mechanisms for the adrenals and gonads are similar, and steroid synthesis in these two glands are the major focus of this review. We will further describe peripheral steroid metabolism and the regulation of steroid hormone potency in target tissues. In addition, we will briefly discuss the congenital adrenal hyperplasias to illustrate the principles developed in the initial sections. Finally, we will discuss some recent developments in steroidogensis, focusing on cytochrome P450 oxidoreductase deficiency and the alternate or "backdoor" pathway to dihydrotestosterone. We will conclude with a description of aberrant signaling mechanisms observed in adrenal tumors as a further example of how these pathways can be disturbed in pathologic states.

The chimeric CYP21P/CYP21 gene and 21-hydroxylase deficiency

The chimeric CYP21P/CYP21 gene is a consequence of a 26- or 32-kb deletion in the C4-CYP21 repeat module of CYP21P, tenascin A ( XA), serine/threonine nuclear protein kinase ( RP2), and the C4B and CYP21 genes in congenital adrenal hyperplasia (CAH) with steroid 21-hydroxylase deficiency. To date, there have been three distinct chimeras found in CAH patients in ethnic Chinese. Initiation for production of these molecules is proposed to be chi-like sequences and a minisatellite consensus existing in several noncoding regions in CYP21 genes. These molecules have the 5' end of the CYP21P-specific sequence in common but differ in the 3' end of CYP21-specific genes. In addition, there appears to be a 3.2-kb fragment generated by Taq I digestion, which leads to allele dropout in PCR amplification for detecting the aberrant splicing site of the IVS2 -12A/C>G mutation at nucleotide (nt) 655 in the CYP21 gene. Therefore, the chimeric CYP21P/CYP21 cannot be detected by conventional methods. It has been demonstrated that a PCR product amplified with allele-specific primers covering tenascin B ( TNXB) to the 5' end of the CYP21 gene combined with Southern analysis by Ase I and Nde I digestion may be used for identifying the chimera in the CYP21 gene.

A novel cDNA detects homozygous microdeletions in greater than 50% of type I spinal muscular atrophy patients

Spinal muscular atrophy (SMA) is the second most common lethal, autosomal recessive disease in Caucasians (after cystic fibrosis). Childhood SMAs are divided into three groups (type I, II and III), which are allelic variants of the same locus in a region of approximately 850 kb in chromosome 5q12-q13, containing multiple copies of a novel, chromosome 5-specific repeat as well as many atypical pseudogenes. This has hampered the identification of candidate genes. We have identified several coding sequences unique to the SMA region. A genomic fragment detected by one cDNA is homozygously deleted in 17/29 (58%) of type I SMA patients. Of 235 unaffected individuals examined, only two showed the deletion and both are carriers of SMA. Our results suggest that deletion of at least part of this novel gene is directly related to the phenotype of SMA.

A recombination-based transgenic mouse system for genotoxicity testing

It is well established that mutagens induce recombination in cultured cells and experimental organisms. Presumably, this is a consequence of the DNA-damage-triggering cellular-repair mechanisms. The relationship between recombination and mutagenicity has been exploited in submammalian organisms, such as yeast, to assay the ability of chemical agents and radiation to induce a form of recombination called gene conversion--the non-reciprocal transfer of genetic information. This work has demonstrated the efficacy of predicting mutagenicity on the basis of recombination induction. Here, we describe the utilization of a transgenic mouse system for efficient detection of germ-line gene-conversion events as a mutagen-screening tool. These mice contain two mutually defective reporter (lacZ) genes under the regulatory control of a spermatogenesis-specific promoter. A particular intrachromosomal gene conversion event must occur for the generation of functional lacZ activity. Conversion events are visualized by histochemical staining or flow cytometric analysis of transgenic spermatids. The highly mutagenic compound chlorambucil induced a several fold percentage-wise increase of lacZ-positive spermatids, whereas acrylamide, a weak genotoxin, produced no marked increase in converted spermatids. The results indicate that recombination-based transgenic mouse models for genotoxin screening present a viable option for inexpensive and rapid whole-animal mutagen testing. The particular mice we describe may ultimately prove to be a useful tool for identifying agents which can cause heritable genetic mutations in humans.

Prenatal diagnosis and treatment of 21-hydroxylase deficiency

Prenatal diagnosis of 21-hydroxylase deficiency, the most common cause of congenital adrenal hyperplasia (CAH), has benefited from the advances in endocrinologic and molecular genetic studies. In 1976, prenatal diagnosis of the disease was first attempted by measuring 17-hydroxyprogesterone in the amniotic fluid in the second trimester of pregnancy. Discovery of a close linkage between HLA and the disease gave a second approach for prenatal diagnosis, the latter being made by linkage study of the haplotypes of the index case in a given family. Diagnosis was later made directly by molecular biology. Currently, the studies of the C4-CYP21B gene locus by Southern blotting and the CYP21B gene mutations by PCR methods simplify the diagnostic procedure of an early and accurate prenatal diagnosis in the first trimester. In these conditions all families are now informative. Moreover, using a direct genetic analysis associated with the possibility of detecting the heterozygotes in a non-related CAH population, a prenatal diagnosis can be done in a family without a previously CAH affected child. From our results in a series of 274 pregnancies at risk for CAH in whom prenatal diagnosis has been made by these different approaches, it can be concluded that steroid analysis in the amniotic fluid is an accurate method but provides only a late (second trimester) diagnosis, while an early and accurate diagnosis now relies on adequate molecular genetic studies on chorion villus biopsies. In the aim to prevent the virilization of the external genitalia in CAH female fetuses, prenatal treatment was instituted in our group in 1979 by giving dexamethasone to the mother. This prenatal treatment appears safe for the fetus and the child and is effective in preventing virilization of CAH affected females. Although the degree of prevention is not always complete in all cases, the advantages of prenatal treatment are prevailing over the complications observed in a few mothers.

Analysis of the duplicated human C4/P450c21/X gene cluster

Gene duplications, deletions and rearrangements occur with an unusually high frequency in the region of the P450c21 genes encoding 21-hydroxylase. In the human genome, the locus contains at least 6 genes, oriented 5' C4A, P450c21A, XA, C4B, P450c21B, XB 3'. Sequence analysis of the XA gene, of the 5' flanking DNA of the C4A gene, and of part of the XB gene revealed that this gene cluster was duplicated by nonhomologous recombination at a CAAG tetranucleotide. The location of this duplication suggests that it may have occurred after mammalian speciation. The XA gene is abundantly expressed in the human adrenal as a stable 2.6 kb RNA, but it is not known if that RNA serves a biological function. Knowledge of the anatomy of the XA gene facilitates genetic analysis of disease-causing lesions in the P450c21B gene. Southern blotting data show that about 76% of disordered P450c21B alleles bear gene microconversions that resemble point mutations; the remaining alleles are equally distributed between gene deletions and large gene conversions.

Hormonal profiles in Italian late-onset adrenal hyperplasia correlate with HLA class III polymorphisms

To investigate the genetic polymorphisms of the HLA region in late-onset adrenal hyperplasia, 13 Italian patients affected by the disease were analyzed for: (1) HLA-A and -B typing; (2) restriction fragment length polymorphism (RFLP) of DR beta, DQ beta, DQ alpha, 21-hydroxylase A and B genes; (3) fourth complement fraction loci A and B (C4A and C4B), second complement fraction (C2) and properdin B factor (Bf) complement typing; (4) hormonal characteristics associated with some HLA haplotypes. HLA alleles B14 and DR beta 1 were found to be significantly more frequent in patients with respect to controls (relative risk: 8.7 and 7.2, p less than 0.001 and p less than 0.0001, respectively). Also C4B*2, 1 duplication was more frequent in patients than in normal subjects (23% vs. 1.5%, p less than 0.0001). Moreover, patients carrying a duplicated C4B (as well as those having the B14 antigen) showed higher 17-hydroxyprogesterone levels after ACTH stimulation. RFLP analysis of 21-hydroxylase genes with a specific probe revealed a duplication of 21-hydroxylase A gene in 40% of patients. All these individuals carried the C4A*2 B*2,1 phenotype and 75% of them displayed a clearly recognizable duplication at the C4B locus. These data support the hypothesis that in late-onset adrenal hyperplasia the 21-hydroxylase A pseudogene, even if inactive, may play a negative role in the regulation of 21-hydroxylase biosynthesis. Furthermore, we suggest analyzing class III phenotypes to screen the enzymatic defect.

Rapid identification of deoxyribonucleic acid sequence differences in cytochrome P-450 21-hydroxylase (CYP21) genes with denaturing gradient gel blots

Denaturing gradient gel electrophoresis was used to identify single-base differences in the cytochrome P-450 21-hydroxylase (CYP21) genes of 132 unrelated control individuals and family members of three unrelated patients with 21-hydroxylase deficiency. The salt-wasting variety was caused by gene deletion and gene conversion/deletion mutations in affected members of two families studied. The simple virilizing form, present in the third family, was caused by an apparent point mutation not detectable by routine Southern blots. We have detected many restriction fragment melting polymorphisms in the CYP21 genes of the members of both salt-wasting families and normal individuals with denaturing gradient gel electrophoresis. We also identified a restriction fragment melting polymorphism specific for the simple virilizing patient in the third family. The data demonstrate that the CYP21 genes are highly polymorphic and that denaturing gradient gel electrophoresis is useful for genomic deoxyribonucleic acid analysis of patients with 21-hydroxylase deficiency.

Normal genes for the cholesterol side chain cleavage enzyme, P450scc, in congenital lipoid adrenal hyperplasia

Congenital lipoid adrenal hyperplasia is the most severe form of congenital adrenal hyperplasia. Affected individuals can synthesize no steroid hormones, and hence are all phenotypic females with a severe salt-losing syndrome that is fatal if not treated in early infancy. All previous studies have suggested that the disorder is in the cholesterol side chain cleavage enzyme (P450scc), which converts cholesterol to pregnenolone. A newborn patient was diagnosed by the lack of significant concentrations of adrenal or gonadal steroids either before or after stimulation with corticotropin (ACTH) or gonadotropin (hCG). The P450scc gene in this patient and in a previously described patient were grossly intact, as evidenced by Southern blotting patterns. Enzymatic (polymerase chain reaction) amplification and sequencing of the coding regions of their P450scc genes showed these were identical to the previously cloned human P450scc cDNA and gene sequences. Undetected compound heterozygosity was ruled out in the new patient by sequencing P450scc cDNA enzymatically amplified from gonadal RNA. Northern blots of gonadal RNA from this patient contained normal sized mRNAs for P450scc and also for adrenodoxin reductase, adrenodoxin, sterol carrier protein 2, endozepine, and GRP-78 (the precursor to steroidogenesis activator peptide). These studies show that lipoid CAH is not caused by lesions in the P450scc gene, and suggest that another unidentified factor is required for the conversion of cholesterol to pregnenolone, and is disordered in congenital lipoid adrenal hyperplasia.

Hormonal patterns in a successful pregnancy of a patient with late-onset 21-OH deficiency taking methylprednisolone; a case report

A successful pregnancy of a young woman with late-onset congenital adrenal hyperplasia (LOCAH) is reported. Exogenous glucocorticoids are the most commonly used regimen in such cases both for suppression of adrenal overstimulation and avoiding masculinization of a female fetus. In our LOCAH patient methylprednisolone has been used for treatment. We present the management and the outcome of this pregnancy, as well as the hormonal follow-up.

Aldosterone synthesis in salt-wasting congenital adrenal hyperplasia with complete absence of adrenal 21-hydroxylase

BACKGROUND

Congenital adrenal hyperplasia due to 21-hydroxylase deficiency is a disorder of cortisol and aldosterone biosynthesis that results from mutations in the CYP21 gene encoding the adrenal 21-hydroxylase P-450c21. It can cause severe salt wasting in newborns that requires long-term treatment with glucocorticoids and mineralocorticoids. We describe a spontaneous partial recovery from this disorder in a 19-year-old woman who had discontinued treatment.

METHODS

We measured plasma and urinary levels of adrenal hormones, plasma renin activity, and sodium balance longitudinally in the patient and four other patients in whom adrenal hyperplasia had been diagnosed in infancy and in whom DNA analysis had predicted a complete absence of functional P-450c21. The ratio of plasma renin activity to urinary aldosterone was used as a measure of the response of the adrenal zona glomerulosa. Two patients underwent intravenous infusion of [3H]progesterone for the measurement of extraadrenal production of 21-hydroxylated precursors of aldosterone.

RESULTS

The patient who had discontinued her medication excreted a normal amount of aldosterone (20.0 nmol per square meter of body-surface area per day) while following a diet low in sodium. Her ratio of plasma renin activity to urinary aldosterone-18-glucuronide excretion was 1.7 after three days of sodium restriction, as compared with a ratio of 4.7 at the age of nine years (normal range, 0.03 to 0.1). The percentage of extraadrenal conversion of progesterone to deoxycorticosterone was low. The four other patients had variable responses to sodium restriction after the neonatal period (range for plasma renin activity:urinary aldosterone-18-glucuronide, 1.9 to 19.4).

CONCLUSIONS

Although patients with salt-wasting 21-hydroxylase deficiency have functionally equivalent mutations in their CYP21 genes, they may vary from one another and over time in their ability to produce mineralocorticoids. This variation may be attributable to another adrenal enzyme with 21-hydroxylase activity.

Sodium chloride supplement at diagnosis and during infancy in children with salt-losing 21-hydroxylase deficiency

Eight infants (6 female, 2 male) with salt-losing congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency were studied to determine the sodium deficit at diagnosis and the level of salt supplement required in addition to subsequent hormone replacement. The median sodium deficit at diagnosis was 34 mmol (range 16-78) or 10.5 mmol/kg (range 4-24). A mean sodium supplement of 2.2 mmol/kg per day (range 0.5-4.9), double the amount provided with feeds, was required to maintain plasma sodium concentration and plasma renin activity (PRA) in the normal range for age. We present an equation based on sodium output (urine), sodium input (feeding plus supplement) and plasma sodium concentration to calculate the sodium supplement needed to maintain sodium balance on hormone replacement in this condition and some practical management suggestions. The necessity for salt supplements is often underestimated and the salt-losing tendency exacerbated by infection remains an unnecessary reason for hospitalization during the first months of life. In patients with salt-losing CAH life-long mineralocorticoid treatment is necessary but additional salt supplements are needed to maintain plasma sodium concentration and PRA in the normal range during infancy.

Improved test to identify heterozygotes for congenital adrenal hyperplasia without index case examination

In an attempt to improve detection of heterozygote carriers of the gene for congenital adrenal hyperplasia (21-hydroxylase deficiency; CAH) 64 families with at least 1 affected member (72 homozygotes and 191 clinically healthy subjects) were studied by HLA genotyping and by the single-dose corticotropin stimulation test. Plasma samples were drawn immediately before corticotropin and 60 min after its injection, and they were analysed simultaneously for eight adrenal steroids by radioimmunoassay after extraction and automated gel chromatography. Heterozygosity was defined as the presence of one HLA haplotype in common with the affected relative. Of the various basal and corticotropin-stimulated steroid levels and their ratios, the ratio of 17-hydroxyprogesterone to 11-deoxycorticosterone after corticotropin had the greatest power to discriminate between heterozygotes and normal relatives; that ratio was significantly higher in the heterozygotes (n = 116) than in the normal relatives (n = 75) and there was no overlap between the groups (range 12.2-214 vs 1.2-11.9). Thus, it is possible to detect all CAH heterozygotes without examining the index case by means of specific steroid analysis.

Pseudogene/functional gene ratio in late-onset 21-hydroxylase-deficient adrenal hyperplasia

Late-onset adrenal hyperplasia caused by 21-hydroxylase deficiency leads to hyperandrogenic symptoms in 1% to 6% of hyperandrogenic women. Normally there are two 21-hydroxylase genes present in a 1:1 ratio. Gene CYP21A is a nonfunctional pseudogene, whereas CYP21B is an active gene. Abnormalities of the CYP21A/CYP21B gene ratio may serve as a marker for late-onset adrenal hyperplasia. Eight hyperandrogenic patients with late-onset adrenal hyperplasia and five control subjects were studied by evaluation of autoradiograms of Taq I and Kpn I digests by means of laser densitometry. Seven of eight (87%) patients with late-onset adrenal hyperplasia had an abnormal CYP21A/CYP21B gene ratio on laser densitometry, suggestive of CYP21A gene duplication, CYP21B gene deletion, or the conversion of a CYP21B gene to a CYP21A gene. One of the five control subjects had a heterozygous deletion of the CYP21A gene. The CYP21A/CYP21B gene ratio may serve as a useful genetic marker for late-onset adrenal hyperplasia in a non-high-risk population.