A new marker for early diagnosis of 21-hydroxylase deficiency: 3beta,16alpha,17alpha-trihydroxy-5alpha-pregnane-7,20-dione

The interpretation of immunometric, chromatographic and mass spectrometric data for steroids in diagnosis of endocrine disorders

The analysis of steroids for endocrine disorders is in transition from immunoassay of individual steroids to more specific chromatographic and mass spectrometric methods with simultaneous determination of several steroids. Gas chromatography (GC) and liquid chromatography (LC) coupled with mass spectrometry (MS) offer unrivalled analytical capability for steroid analysis. These specialist techniques were often judged to be valuable only in a research laboratory but this is no longer the case. In a urinary steroid profile up to 30 steroids are identified with concentrations and excretion rates reported in a number of ways. The assays must accommodate the wide range in steroid concentrations in biological fluids from micromolar for dehydroepiandrosterone sulphate (DHEAS) to picomolar for oestradiol and aldosterone. For plasma concentrations, panels of 5-20 steroids are reported. The profile results are complex and interpretation is a real challenge in order to inform clinicians of likely implications. Although artificial intelligence and machine learning will in time generate reports from the analysis this is a way off being adopted into clinical practice. This review offers guidance on current interpretation of the data from steroid determinations in clinical practice. Using this approach more laboratories can use the techniques to answer clinical questions and offer broader interpretation of the results so that the clinician can understand the conclusion for the steroid defect, and can be advised to program further tests if necessary and instigate treatment. The biochemistry is part of the patient workup and a clinician led multidisciplinary team discussion of the results will be required for challenging patients. The laboratory will have to consider cost implications, bearing in mind that staff costs are the highest component. GC-MS and LC-MS/MS analysis of steroids are the choices. Steroid profiling has enormous potential to improve diagnosis of adrenal disorders and should be adopted in more laboratories in favour of the cheap, non-specific immunological methods.

Using Machine Learning to Aid the Interpretation of Urine Steroid Profiles

BACKGROUND

Urine steroid profiles are used in clinical practice for the diagnosis and monitoring of disorders of steroidogenesis and adrenal pathologies. Machine learning (ML) algorithms are powerful computational tools used extensively for the recognition of patterns in large data sets. Here, we investigated the utility of various ML algorithms for the automated biochemical interpretation of urine steroid profiles to support current clinical practices.

METHODS

Data from 4619 urine steroid profiles processed between June 2012 and October 2016 were retrospectively collected. Of these, 1314 profiles were used to train and test various ML classifiers' abilities to differentiate between “No significant abnormality” and “?Abnormal” profiles. Further classifiers were trained and tested for their ability to predict the specific biochemical interpretation of the profiles.

RESULTS

The best performing binary classifier could predict the interpretation of No significant abnormality and ?Abnormal profiles with a mean area under the ROC curve of 0.955 (95% CI, 0.949–0.961). In addition, the best performing multiclass classifier could predict the individual abnormal profile interpretation with a mean balanced accuracy of 0.873 (0.865–0.880).

CONCLUSIONS

Here we have described the application of ML algorithms to the automated interpretation of urine steroid profiles. This provides a proof-of-concept application of ML algorithms to complex clinical laboratory data that has the potential to improve laboratory efficiency in a setting of limited staff resources.

The evolution of methods for urinary steroid metabolomics in clinical investigations particularly in childhood

The metabolites of cortisol, and the intermediates in the pathways from cholesterol to cortisol and the adrenal sex steroids can be analysed in a single separation of steroids by gas chromatography (GC) coupled to MS to give a urinary steroid profile (USP). Steroids individually and in profile are now commonly measured in plasma by liquid chromatography (LC) coupled with MS/MS. The steroid conjugates in urine can be determined after hydrolysis and derivative formation and for the first time without hydrolysis using GC-MS, GC-MS/MS and liquid chromatography with mass spectrometry (LC-MS/MS). The evolution of the technology, practicalities and clinical applications are examined in this review. The patterns and quantities of steroids changes through childhood. Information can be obtained on production rates, from which children with steroid excess and deficiency states can be recognised when presenting with obesity, adrenarche, adrenal suppression, hypertension, adrenal tumours, intersex condition and early puberty, as examples. Genetic defects in steroid production and action can be detected by abnormalities from the GC-MS of steroids in urine. New mechanisms of steroid synthesis and metabolism have been recognised through steroid profiling. GC with tandem mass spectrometry (GC-MS/MS) has been used for the tentative identification of unknown steroids in urine from newborn infants with congenital adrenal hyperplasia. Suggestions are made as to areas for future research and for future applications of steroid profiling. As routine hospital laboratories become more familiar with the problems of chromatographic and MS analysis they can consider steroid profiling in their test repertoire although with LC-MS/MS of urinary steroids this is unlikely to become a routine test because of the availability, cost and purity of the internal standards and the complexity of data interpretation. Steroid profiling with quantitative analysis by mass spectrometry (MS) after chromatography now provides the most versatile of tests of adrenal function in childhood.

17-Hydroxyprogesterone in children, adolescents and adults

17-Hydroxyprogesterone (17-OHP) is an intermediate steroid in the adrenal biosynthetic pathway from cholesterol to cortisol and is the substrate for steroid 21-hydroxylase. An inherited deficiency of 21-hydroxylase leads to greatly increased serum concentrations of 17-OHP, while the absence of cortisol synthesis causes an increase in adrenocorticotrophic hormone. The classical congenital adrenal hyperplasia (CAH) presents usually with virilisation of a girl at birth. Affected boys and girls can have renal salt loss within a few days if aldosterone production is also compromised. Diagnosis can be delayed in boys. A non-classical form of congenital adrenal hyperplasia (NC-CAH) presents later in life usually with androgen excess. Moderately raised or normal 17-OHP concentrations can be seen basally but, if normal and clinical suspicion is high, an ACTH stimulation test will show 17-OHP concentrations (typically >30 nmol/L) above the normal response. NC-CAH is more likely to be detected clinically in females and may be asymptomatic particularly in males until families are investigated. The prevalence of NC-CAH in women with androgen excess can be up to 9% according to ethnic background and genotype. Mutations in the 21-hydroxylase genes in NC-CAH can be found that have less deleterious effects on enzyme activity. Other less-common defects in enzymes of cortisol synthesis can be associated with moderately elevated 17-OHP. Precocious puberty, acne, hirsutism and subfertility are the commonest features of hyperandrogenism. 17-OHP is a diagnostic marker for CAH but opinions differ on the role of 17OHP or androstenedione in monitoring treatment with renin in the salt losing form. This review considers the utility of 17-OHP measurements in children, adolescents and adults.

21-hydroxylase deficiency in the neonate - trends in steroid anabolism and catabolism during the first weeks of life

Deficiency of 21-hydroxylase provides an in vivo model of intrauterine induction of enzymes participating in steroid anabolism and catabolism. Quantitative data for 93 steroid metabolites in urine from 111 patients and 7 controls (25 samples) were compared over the first six weeks of life. Net flux through the key anabolic enzymes was examined by comparison of the totals of steroids derived from the intermediates prior to and following each enzymatic step. Metabolic relationships were established on structural grounds and by Pearson correlation. The relative importance of each catabolic route was evaluated after summing metabolites classified according to their structure as fetal, neonatal, and classical (adult) type. Hierarchical cluster analysis identified the structure at C3-C5 as a key distinguishing feature of the major catabolic streams and demonstrated a split point in metabolic pattern in patients at 7 days. Changes with time in steroid metabolism, larger in patients than in controls, could be interpreted as reflecting increased cortisol demand post partum, the clinical onset of salt-wasting and a transition in catabolism from fetal to postnatal life. Faster involution of the fetal zone and pronounced enhancement of steroid production in zona fasciculata and zona glomerulosa were indicated in patients. Predominant at birth were 'planar' fetal-type 5α-reduced metabolites, adapted to placental excretion, which gave way to additionally hydroxylated neonatal-type metabolites, facilitating renal excretion. Classical metabolism made gains over the study period. Overproduction of steroids in utero in 21-hydroxylase deficiency would have induced fetal catabolic pathways dependent on 5α-reduction. A progressive increase of steroids likely to arise from 5α-reductase type 2 activity, again more distinct in disease, was observed. We demonstrate that the key intermediates in the hypothetical 'backdoor' pathway of androgen synthesis are part of a broader catabolic network and should not be examined in isolation.

Steroids excreted in urine by neonates with 21-hydroxylase deficiency. 3. Characterization, using GC-MS and GC-MS/MS, of androstanes and androstenes

Urine from neonates with 21-hydroxylase deficiency contains a large range of androstane(ene)s, many of which have not been previously described. We present their characterization as the third part of a comprehensive study of urinary steroids, aiming to enhance the diagnosis of this disorder and to further elucidate steroid metabolism in neonates. Steroids were analyzed, after extraction and enzymatic conjugate hydrolysis, as methyloxime-trimethylsilyl ether derivatives on gas-chromatographs coupled to quadrupole and ion-trap mass-spectrometers. GC-MS and GC-MS/MS spectra were used together to determine the structure of hitherto undescribed androstane(ene)s. GC-MS/MS was pivotal for the structural characterization of 2-hydroxylated androstenediones but GC-MS was generally more informative for androstane(ene)s, in contrast to 17-hydroxylated pregnane(ene)s. Parallels were found between the GC-MS and GC-MS/MS characteristics of structurally similar androstenediones and progesterones without a substituent on the D-ring, but not with those of 17-hydroxylated progesterones. Assignment of 5α(β) orientation, based on GC-MS characteristics, was possible for 11-oxo-androstanes. The major endogenous 3β-hydroxy-5-enes in 21-hydroxylase deficiency did not differ from those in unaffected neonates. The key qualitative and quantitative differences encompassed 5α(β)-androstanes and 3-oxo-androst-4-enes. Major positions of hydroxylation in these were C(2), C(6), C(11), C(16) and C(18). Additional oxo-groups were common at C(6), C(11) and C(16). We conclude that the presence of multiple further oxygenated metabolites of androstenedione in urine from neonates with 21-hydroxylase deficiency and their pattern indicate a predominance of the classical pathway of androgen synthesis and reflect an increased demand for clearance. The positions of oxygenation in androstane(ene)s are dependent on the configuration at C(3)-C(5).

Steroids excreted in urine by neonates with 21-hydroxylase deficiency. 2. Characterization, using GC-MS and GC-MS/MS, of pregnanes and pregnenes with an oxo- group on the A- or B-ring

Urine from neonates with 21-hydroxylase deficiency contains a large range of metabolites of 17-hydroxyprogesterone, 21-deoxycortisol and androgens but few have been previously described. We present the second part of a comprehensive project to characterize and identify these in order to enhance diagnosis and to further elucidate neonatal steroid metabolism. Steroids were analyzed, after extraction and enzymatic conjugate hydrolysis, as methyloxime-trimethylsilyl ether derivatives on gas-chromatographs coupled to quadrupole and ion-trap mass-spectrometers. GC-MS and GC-MS/MS spectra were used together to determine the structure of the A- and B-rings containing an oxo group. Fragmentations indicating presence of 3-, 6-, and 7-oxo groups and also 1β-, 2α-, 4β-, and 6β-hydroxyls are presented and discussed for the first time. Interpretation was aided by comparison with spectra of available relevant standards, of oxidation products of standards and urinary metabolites and of deuterated derivatives. Endogenous 1-enes and 2(3)-ene artifacts of non-hydrolyzed 3α-sulfates are also reported. D-ring and side chain structure was determined according to our previously published criteria. Likely metabolic relationships were also explored. We conclude that GC-MS combined with GC-MS/MS allows identification of the A- and B-ring structure of pregnane and pregnenes in the presence of an oxo group on one of these rings. Major oxygenations are 1β, 15β, 16α and 21-hydroxy and 6- and 7-oxo groups. Minor positions of hydroxylation are those at 2α, 4β and 6β. Three major metabolic streams exist in affected neonates in addition to the classical 3α-hydroxy-5β-pregnane pathway, i.e. these of the 3-oxo-4-enes as well as 3α- and 3β-hydroxy-5α-anes.

Challenges and benefits of endogenous steroid analysis by LC–MS/MS

Quantification of endogenous hormonal steroids and their precursors is essential for diagnosing a wide range of endocrine disorders. Historically, these analyses have been carried out using immunoassay, but such methods are problematic, especially for low-concentration analytes, due to assay interference by other endogenous steroids. MS offers improved specificity over immunoassay and can be highly sensitive. GC–MS, with use of stable isotopically labeled internal standards, is considered the ‘gold standard’ method for serum steroid analysis. GC–MS is the method of choice for profiling steroid metabolites in urine, but these techniques are not appropriate for routine use in clinical laboratories owing to a need for extensive sample preparation, as well as analytical expertise. LC–MS/MS compares well to GC–MS in terms of accuracy, precision and sensitivity, but allows simplified sample preparation. While most publications have featured only one or a limited number of steroids, we consider that steroid paneling (which we propose as the preferred term for multitargeted steroid analysis) has great potential to enable clinicians to make a definitive diagnosis. It is adaptable for use in a number of matrices, including serum, saliva and dried blood spots. However, LC–MS/MS-based steroid analysis is not straightforward, and understanding the chemical and analytical processes involved is essential for implementation of a robust clinical service. This article discusses specific challenges in the measurement of endogenous steroids using LC–MS/MS, and provides examples of the benefits it offers.

Transformation of a series of saturated isomeric steroidal diols by Aspergillus tamarii KITA reveals a precise stereochemical requirement for entrance into the lactonization pathway

Four isomers of 5α-androstan-3,17-diol have been transformed by the filamentous fungus Aspergillus tamarii, an organism which has the ability to convert progesterone to testololactone in high yield through an endogenous four step enzymatic pathway. The only diol handled within the lactonization pathway was 5α-androstan-3α,17β-diol which, uniquely underwent oxidation of the 17β-alcohol to the 17-ketone prior to its Baeyer-Villiger oxidation and the subsequent production of 3α-hydroxy-17a-oxa-D-homo-5α-androstan-17-one. This demonstrated highly specific stereochemical requirements of the 17β-hydroxysteroid dehydrogenase for oxidation of this specific steroidal diol to occur. In contrast, the other three diols were transformed within the hydroxylation pathway resulting in functionalization at C-11β. Only 5α-androstan-3β,17α-diol could bind to the hydroxylase in multiple binding modes undergoing monohydroxylation in 6β and 7β positions. Evidence from this study has indicated that hydroxylation of saturated steroidal lactones may occur following binding of ring-D in its open form in which an α-alcohol is generated with close spatial parity to the C-17α hydroxyl position. All metabolites were isolated by column chromatography and were identified by (1)H, (13)C NMR and DEPT analysis and further characterized using infra-red, elemental analysis and accurate mass measurement.