Inborn errors of adrenal steroidogenesis

Monogenic mineralocorticoid hypertension

Monogenic mutations leading to excessive activation of the mineralocorticoid pathway result, almost always, in suppressed renin and hypertension in adult life and sometimes in hypokalaemia and alkalosis, which can be severe. In most of these syndromes, precise molecular changes in specific steroidogenic or effector genes have been identified, permitting appreciation of (1) pathophysiology, (2) great diversity of phenotype and (3) possibility of genetic methods of diagnosis. Yet to be achieved elucidation of the genetic basis of familial hyperaldosteronism type II, the most common and clinically significant of them, will enhance detection of primary aldosteronism, currently the commonest specifically treatable and potentially curable form of hypertension. While classic, complete-phenotype presentations of monogenic forms of mineralocorticoid hypertension are rarely recognised, more subtle genetic expression causing less florid manifestations could represent a significant proportion of so-called 'essential hypertension.'

Genotyping of five chinese patients with 17alpha-hydroxylase deficiency diagnosed through high-performance liquid chromatography serum adrenal profile: identification of two novel CYP17 mutations

CONTEXT

17alpha-Hydroxylase deficiency is a rare form of congenital adrenal hyperplasia caused by CYP17 gene mutations.

OBJECTIVE

Five Chinese patients with 17alpha-hydroxylase deficiency were genotyped.

PATIENTS

The five patients derived from four families living in Shandong Province, China. The diagnosis of 17alpha-hydroxylase deficiency was initially established through HPLC serum adrenal profiles in Qilu Hospital, China, from 1983-1993.

RESULTS

Three CYP17 gene mutations were identified from these patients. Among them, V311fs and Y329fs are two novel frame-shifting mutations. V311fs is an 8-bp nucleotide (TTAAATGG) deletion in exon 5. Y329fs is a deletion-insertion combined mutation (TAC-->AA) at codon 329 in exon 6. Two homozygotes for Y329fs and one compound heterozygote for Y329fs and V311fs were identified from three different families. Two homozygous sisters for the D487_S488_F489 deletion were identified.

CONCLUSION

The results confirmed the diagnostic value of the HPLC serum adrenal profile for 17alpha-hydroxylase deficiency. The D487_S488_F489 deletion had been identified in two previously genotyped Chinese families. In our present study, a third Chinese family with this mutation was identified, suggesting that this mutation is a prevalent CYP17 mutation in the Chinese population. The identification of Y329fs mutation in addition to three previously identified mutations at codon 329 suggests that codon 329 is an unstable point of the CYP17 gene. The mutations identified from our five patients appear to be random, but the recurrence of the Y329fs mutation may be attributed to a founder effect. Our studies suggest that 17alpha-hydroxylase deficiency may not be rare in the Chinese population.

Inherited sodium avid states

Several familial forms of hypertension have been identified, in which the mendelian pattern of inheritance indicated that hypertension results from the alteration of a single gene. This short review focuses on those rare monogenic disorders characterized by a low-renin profile. This common feature reflects that the causative mutations responsible for these disorders all result in an excessive sodium reabsorption in the aldosterone-dependent nephron. Low-renin familial hypertensions with hypokalemia encompass familial hyperaldosteronisms, in which aldosterone levels are elevated, and familial pseudohyperaldosteronisms, mimicking aldosteronism despite appropriately suppressed aldosterone levels. In these disorders, the avidity of the kidney for sodium is because of dysregulated sodium reabsorption through the epithelial sodium channel ENaC and results in potassium wasting and metabolic alcalosis. Familial hypertension with hyperkalemia is a specific syndrome resulting from mutations in at least 3 different genes, among which 2 have been recently identified. These genes encode members of a new family of kinase, the WNK kinases, involved in the regulation of sodium and potassium excretion by the kidney.

[Genes involved in sex determination and differentiation]

Chromosomal sex is established at fertilization by the presence of an X or Y chromosome. The first step of male and female development is gonadal specialization in testes or ovaries; all other processes that follow result from secondary effects produced by testis and ovary hormones. Gonadal determination and differentiation and the development of external genitalia involve time- and tissue-specific expression of genes forming a gene cascade. Those genes, their expression profile and their role in the pathological manifestations related to gonadal and external genitalia development will be discussed in this review.

Gender-typed play and amniotic testosterone

Sex differences in play are apparent in a number of mammalian species, including humans. Prenatal testosterone may contribute to these differences. The authors report the first attempt to correlate gender-typed play in a normative sample of humans with measurements of amniotic testosterone (aT). Testosterone was measured in the amniotic fluid of 53 children (31 boys and 22 girls). A strong sex difference was observed in aT and, at ages 4.75 to 5.8 years, on a modified version of the Child Game Participation Questionnaire. Hierarchical regression analyses on the entire group and within-sex correlations suggested that variations in aT did not contribute to individual differences in game participation as reported by the mother. A critique of explanations for this finding is presented.

Mutations in CYP11B1 and congenital adrenal hyperplasia in Moroccan Jews

CONTEXT

In Jews of Moroccan descent (MJ), the prevalence of steroid 11beta-hydroxylase deficiency (11-OHD) is relatively high, with a carrier rate estimated as approximately one in 40. A single mutation in the CYP11B1 gene (encoding 11beta-hydroxylase), R448H, was suggested to account for the disease alleles in this population.

STUDY SUBJECTS

We screened 236 healthy MJ for R448H.

RESULTS

Only two of the subjects screened were found to be carriers, suggesting that the R448H allele frequency is lower than was assumed previously. An R448H/R448C compound heterozygote patient, diagnosed with 11-OHD, was identified. However, a subsequent screen of MJ subjects for R448C failed to detect any carriers, suggesting that this was a private mutation of this family.

CONCLUSION

The high incidence of 11-OHD in MJ, therefore, is only partially explained by the presence of R448H as a founder mutation.

Diagnostic imaging of the thyroid and adrenal glands in childhood

This article reviews the clinical utility of modern imaging techniques, particularly ultrasound (US), CT, and MRI in children with disorders of the thyroid and adrenal glands. Radionuclide scanning is the modality of choice in making the anatomic diagnosis in neonates with congenital hypothyroidism, while US is most useful in defining nodular thyroid disease. CT and MRI of the thyroid tend to be limited to defining the extent of thyroid carcinoma. Adrenal US is an essential step in the differential diagnosis of ambiguous genitalia or salt-losing crises in the newborn, while CT and MRI are more useful in defining the anatomy of the adrenals in older children with tumors or diffuse hyperplasia of the glands.

Haploinsufficiency of cytochrome P450 17alpha-hydroxylase/17,20 lyase (CYP17) causes infertility in male mice

Cytochrome P450 17alpha-hydroxylase/17,20-lyase (CYP17) is critical in determining cortisol and sex steroid biosynthesis. To investigate how CYP17 functions in vivo, we generated mice with a targeted deletion of CYP17. Although in chimeric mice Leydig cell CYP17 mRNA and intratesticular and circulating testosterone levels were dramatically reduced (80%), the remaining testosterone was sufficient to support spermatogenesis as evidenced by the generation of phenotypical black C57BL/6 mice. However, male chimeras consistently failed to generate heterozygous CYP17 mice and after five matings chimeric mice stopped mating indicating a change in sexual behavior. These results suggested that CYP17 deletion caused a primary phenotype (infertility), probably not due to the anticipated androgen imbalance and a secondary phenotype (change in sexual behavior) due to the androgen imbalance. Surprisingly, CYP17 mRNA was found in mature sperm, and serial analysis of gene expression identified CYP17 mRNA in other testicular germ cells. CYP17 mRNA levels were directly related to percent chimerism. Moreover, more than 50% of the sperm from high-percentage chimeric mice were morphologically abnormal, and half of them failed the swim test. Furthermore, 60% of swimming abnormal sperm was devoid of CYP17. These results suggest that CYP17, in addition to its role in steroidogenesis and androgen formation, is present in germ cells where it is essential for sperm function, and deletion of one allele prevents genetic transmission of mutant and wild-type alleles causing infertility followed by change in sexual behavior due to androgen imbalance.

Molecular basis of adrenal insufficiency

Defective production of adrenal steroids due to either primary adrenal failure or hypothalamic-pituitary impairment of the corticotrophic axis causes adrenal insufficiency. Depending on the etiologies of adrenal insufficiency, clinical manifestations may be severe or mild, have gradual or sudden onset, begin in infancy or childhood/adolescence. Adrenal crisis represents an endocrine emergency, and thus the rapid recognition and prompt therapy for adrenal crisis are critical for survival even before the diagnosis is made. The recognition of various disorders that cause adrenal insufficiency, either at a clinical or molecular level, often has implications for the management of the patient. Recent molecular-genetic analysis for the disorder that causes adrenal insufficiency gives valuable insights into the adrenal organogenesis, the regulation of steroid hormone biosynthesis, and the developmental and reproductive endocrinology. In this review we present the latest information on the molecular basis of adrenal insufficiency, with special emphasis on congenital lipoid adrenal hyperplasia, P450-oxidoreductase deficiency, and adrenal hypoplasia congenita.

Practical management of the intersex infant

Intersex occurs when the appearance of the internal or external genitalia is at variance with normal development for either sex. The first question asked by, and of new parents in relation to their offspring is often "Is it a boy or a girl"? A rational approach, based on knowledge of normal prenatal sexual development, and based on a careful physical examination to guide further investigation, is required to reach a diagnosis. We briefly review prenatal sexual development to provide a background to the assessment of genital ambiguity in the newborn. Aspects of physical examination are discussed in detail, with reference to published normative data where possible. We provide a classification of genital ambiguity and an approach to differential diagnosis. We highlight some of the many syndromes associated with genital ambiguity, with reference to their genetic basis where possible. In 46,XX individuals, the commonest cause of genital ambiguity is congenital adrenal hyperplasia due to 21-hydroxylase deficiency; however, in 46,XY individuals the differential diagnosis is wide, and may remain unexplained, even after extensive investigation. Two algorithms are presented, one of which provides an initial approach based on the presence of a uterus and palpable gonads alone, and a second illustrating a comprehensive differential diagnosis of the undervirilised 46,XY individual. We discuss our approach to sharing information on the diagnosis and management with the parents and highlight the early involvement of an experienced multidisciplinary team. Finally, we consider current controversial issues relating to gender assignment and management of genital ambiguity.

Rapid second-tier molecular genetic analysis for congenital adrenal hyperplasia attributable to steroid 21-hydroxylase deficiency

BACKGROUND

Neonatal screening for steroid 21-hydroxylase (CYP21) deficiency is performed to identify congenital adrenal hyperplasia (CAH). The immunologic assay for 17alpha-hydroxyprogesterone (17-OHP) has a high rate of false positives. We assessed the potential for increasing the specificity for CAH by use of a second step involving analysis of the CYP21 gene.

METHODS

Between January 1999 and December 2003, a total of 810,000 newborns were screened. Of these, 7920 had to be retested because their 17-OHP values were above the cutoff of the assay. Sixty-one had positive 17-OHP values in their recall samples and were diagnosed as having CAH. We used a rapid assay for common mutations of the CYP21 gene to analyze these 61 samples. In a prospective study, 198 consecutive samples that had increased 17-OHP and 100 samples that had normal 17-OHP concentrations were genotyped.

RESULTS

Fifty-nine of 61 cases diagnosed as having CAH were confirmed genetically as CYP21 deficiencies. One patient had a 3beta-hydroxysteroid dehydrogenase deficiency, and one patient carried no CYP21 mutations. The 198 increased 17-OHP results were designated as false positives after immunologic testing of recall samples. None of these samples exhibited the genetic pattern consistent with CYP21 deficiency.

CONCLUSIONS

If samples with increased 17-OHP values were screened genetically, the number of retests would decrease by approximately 90%, but the overall sensitivity of CAH screening would remain the same. Adding a second-tier genetic step would require a modest increase in costs, but is counterbalanced by fewer recalls, less clinical follow-up, and a reduction in unnecessary worry for families.

Aging of the Human Adrenal Cortex

The most striking age-related change in the human adrenal cortex is the decline in secretion of dehydroepiandrosterone and its sulfate, steroids synthesized by the inner zone of the cortex, the zona reticularis. Because these steroids are of essentially unknown function, the importance of this age-related change is the subject of considerable debate. It is likely that the age-related change in these steroids results from loss of zona reticularis cells or impairment of their function. During aging, cumulative damage to the zona reticularis could occur through ischemia-related infarcts and other causes of cell death. Cellular senescence could contribute to a loss of the ability of the tissue to replace lost cells. In contrast, feedback mechanisms that regulate adrenocortical growth cause compensatory local tissue hyperplasias called nodules. The effect of imperfect repair of damage combined with compensatory overgrowth in the form of nodules leads to an increasingly abnormal tissue architecture.