Heterozygotes for 17 alpha-hydroxylase deficiency can be detected with a short ACTH test

Steroid metabolism gene variants and their genotype-phenotype correlations in Chinese early-onset hypertension patients

The genetic factors related to early-onset hypertension are largely unknown. This study aimed to determine the spectrum of steroid metabolism gene variants and the clinical relationships of these variants to phenotypes in Chinese patients with early-onset hypertension. A total of 306 consecutive early-onset hypertensive patients were recruited. All coding exons and flanking intronic regions of KCNJ5, CYP11B1, and CYP17A1 were sequenced. Long-distance polymerase chain reaction was used to search for a CYP11B1/CYP11B2 chimeric gene. Pedigree investigations and genotype-phenotype analyses were performed for patients with rare variants. Nine rare variants were detected in eight patients (2.6%), but no CYP11B1/CYP11B2 chimeric gene was identified. One patient and two of her siblings were found to carry compound heterozygous mutations (C183Y and T390R) in CYP17A1 and were eventually diagnosed with atypical congenital adrenal hyperplasia. Patients with rare variants had younger ages of onset [17 (16, 20) vs. 30 (23, 35) years old, p = 0.010] and higher systolic blood pressure (148.5 ± 9.6 vs. 137.9 ± 17.8 mmHg, p = 0.021) than those without rare variants. Additionally, the patients and their relatives carrying rare variants exhibited increased serum free corticosterone [230.4 (7.4, 533.0) vs. 1.9 (0.9, 6.7)ng/ml, p = 0.001] and 11-deoxycorticosterone [16.16 (0.59, 33.23) vs. 0.77 (0.41, 0.96)ng/ml, p = 0.038] levels. Genetic testing is useful for the etiologic diagnosis of early-onset hypertension. Rare variants in steroid metabolism genes were associated with more severe clinical expression and abnormal circulating steroid metabolites in patients with early-onset hypertension.

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.

Identification of steroid biosynthetic defects in genotype-proven heterozygous individuals for 17alpha-hydroxylase/17,20-lyase deficiency

OBJECTIVE

P450c17 deficiency (17alpha-hydroxylase/17,20-lyase deficiency, 17OHD) is a rare form of congenital adrenal hyperplasia caused by CYP17A1 gene mutations. The D487_F489 deletion in exon 8 and Y329fs in exon 6 are relatively frequent mutations of the CYP17A1 gene in China that completely abolish the enzyme activity of P450c17. However, little remains known about steroid biosynthetic functions in carriers with these mutations in a single allele of the CYP17A1 gene, who are assumed to have 50% P450c17 activity. We investigated adrenal steroidogenic function in genotype-proven heterozygotes carrying such mutations in the CYP17A1 gene in vivo.

PATIENTS AND DESIGN

Eight patients and fourteen family members from five families with 17OHD were recruited. The mutations of the CYP17A1 gene in these individuals were screened by sequencing. The hormonal response to cosyntropin (ACTH) was evaluated in the 14 genotype-proven carriers and 45 age- and gender-matched normal controls.

RESULTS

Fourteen carriers of the CYP17A1 mutation - seven with the D487_F489 deletion, six with Y329fs and one with H373L - were identified from the five families with 17OHD. Compared with normal controls, carriers showed lower basal and ACTH-stimulated cortisol levels but higher ACTH-stimulated corticosterone levels. The ratios of corticosterone to cortisol in the genotype-proven heterozygotes were higher than those of the normal controls at the baseline and after cosyntropin stimulation. Similarly, the progesterone levels and the ratios of progesterone to 17-hydroxyprogesterone in the male heterozygotes were also higher than those of the normal controls, both before and after ACTH stimulation.

CONCLUSION

Genotype-proven carriers of the CYP17A1 mutation who lack apparent clinical symptoms exhibit decreased adrenal 17alpha-hydroxylase activity and altered adrenal gland reserve for steroid biosynthesis.

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.

Spontaneous growth and bone age development in a patient with 17alpha-hydroxylase deficiency: evidence of the role of sexual steroids in prepubertal bone maturation

A male pseudohermaphrodite with 17alpha-hydroxylase deficiency and complete nonvirilization was monitored for excessive weight from the age of 3.5 to 11.5 years before the absence of sex steroids was detected. The retrospective analysis of growth data showed retarded bone age development despite adequate growth, which led to a remarkable increase in final height prognosis.

Diagnosis and treatment of 17-hydroxylase deficiency

Leading symptoms of 17-hydroxylase/17,20-lyase deficiency in childhood are hypertension and hypokalemia. We found this enzyme defect in 3 phenotypically female siblings aged 12, 15 and 16 years. Two of the sibs have a 46,XY chromosome pattern, the third is genetically female. Pubertal development did not occur. Both of the 46,XY sibs have male internal and female external genitalia. The 46,XX sister has normal female internal genitalia. At the time of diagnosis, two of the three siblings had hypertension (RR between 190/135 and 160/110 mmHg). Two of the three siblings had low serum potassium and metabolic alkalosis. All three patients had excessively high plasma levels of 11-deoxycorticosterone (DOC) and corticosterone. Aldosterone was also elevated whereas plasma renin activity was suppressed. Plasma cortisol and its 17-hydroxylated precursors were low, as were plasma testosterone, dihydroepiandrosterone sulphate and estradiol, while the gonadotropins LH and FSH were elevated in all three patients. We studied the steroid profiles of these three patients during long term glucocorticoid treatment with dexamethasone, which is now followed for 13 years. Blood pressure and serum potassium became normal. Plasma aldosterone, corticosterone and DOC were clearly lower but not fully normalized. The two genetically male sisters obtained estrogens for induction of female secondary sex characteristics. The third 46,XX sister has normal menstruations during substitution with cyclic estrogen/gestagen therapy. All three patients lack pubic and axillary hair, and reached normal adult heights both for phenotypic sex and for target height. The psychosocial orientation is female in all of them. Apart from rare reports of development of malignant hypertension, prognosis is better than in other enzyme deficiencies causing congenital adrenal hyperplasia since no Addisonian crises occur due to DOC and corticosterone overproduction resulting in apparently normal endogenous glucocorticoid activity.

A neonate with idiopathic hyperaldosteronism

A boy with functional abnormalities of the gastro-intestinal tract, hyponatraemia, hypokalaemia and hypertension is described. All symptoms developed within the first 2 months of life. Increased aldosterone levels were associated with suppressed values in the renin-angiotensin system. The diagnosis of idiopathic hyperaldosteronism was made because of adrenal hyperplasia and the failure to suppress aldosterone to undetectable levels with glucocorticoids. Treatment with spironolactone alone, or in combination with either intravenous dopamine or ibopamine orally, amiloride, enalapril, hydralazine or clonidine corrected serum potassium values but failed to normalize blood pressure and to correct plasma renin activity and plasma aldosterone. However, the combination of spironolactone with nifedipine decreased blood pressure. Abnormal gastro-intestinal motility was corrected by low doses of oral magnesium hydroxide. To assess intracellular calcium homeostasis, the patient's peripheral blood mononuclear cells were incubated with increasing concentrations of calcium. As these cells failed to maintain physiological calcium concentration, a defect in intracellular calcium homeostasis was suspected.

Male pseudohermaphroditism due to 17-hydroxylase deficiency

A 27-year-old phenotypic female presented with primary amenorrhea, severe hypertension, and hypokalemia. At the age of puberty sexual development had not occurred; in particular, sexual hair had not grown. Past history revealed an episode of subarachnoid hemorrhage and several episodes of ventricular tachyarrhythmia. Karyotype was 46, XY. The steroids requiring 17-hydroxylation (cortisol, testosterone, pregnanetriol, 17-ketosteroids, 17-hydroxycorticosteroids) were low, while those not requiring 17-hydroxylation (progesterone, deoxycorticosterone, corticosterone) were high, demonstrating 17-hydroxylase deficiency. The corticosterone/deoxycorticosterone ratio was relatively low, suggesting an associated partial deficiency of 11-hydroxylase.