Radioimmunoassay of blood-spot 17 alpha-hydroxyprogesterone in the management of congenital adrenal hyperplasia

Biochemical monitoring of 21-hydroxylase deficiency: a clinical utility of overnight fasting urine pregnanetriol

PURPOSE OF REVIEW

21-Hydroxylase deficiency (21-OHD), the most common form of congenital adrenal hyperplasia, is an autosomal recessive disorder caused by pathogenic variants in CYP21A2. Although this disorder has been known for several decades, many challenges related to its monitoring and treatment remain to be addressed. The present review is written to describe an overview of biochemical monitoring of this entity, with particular focus on overnight fasting urine pregnanetriol.

RECENT FINDINGS

We have conducted a decade-long research project to investigate methods of monitoring 21-OHD in children. Our latest studies on this topic have recently been published. One is a review of methods for monitoring 21-OHD. The other was to demonstrate that measuring the first morning PT level may be more practical and useful for biochemical monitoring of 21-OHD. The first morning pregnanetriol (PT), which was previously reported to reflect a long-term auxological data during the prepubertal period, correlated more significantly than the other timing PT in this study, with 17-OHP, before the morning medication.

SUMMARY

In conclusion, although the optimal method of monitoring this disease is still uncertain, the use of overnight fasting urine pregnanetriol (P3) as a marker of 21-OHD is scientifically sound and may be clinically practical.

Monitoring treatment in pediatric patients with 21-hydroxylase deficiency

21-hydroxylase deficiency (21-OHD) is the most common form of congenital adrenal hyperplasia. In most developed countries, newborn screening enables diagnosis of 21-OHD in asymptomatic patients during the neonatal period. In addition, recent advances in genetic testing have facilitated diagnosing 21-OHD, particularly in patients with equivocal clinical information. On the other hand, many challenges related to treatment remain. The goals of glucocorticoid therapy for childhood 21-OHD are to maintain growth and maturation as in healthy children by compensating for cortisol deficiency and suppressing excess adrenal androgen production. It is not easy to calibrate the glucocorticoid dosage accurately for patients with 21-OHD. Auxological data, such as height, body weight, and bone age, are considered the gold standard for monitoring of 21-OHD, particularly in prepuberty. However, these data require months to a year to evaluate. Theoretically, biochemical monitoring using steroid metabolites allows a much shorter monitoring period (hours to days). However, there are many unsolved problems in the clinical setting. For example, many steroid metabolites are affected by the circadian rhythm and timing of medication. There is still a paucity of evidence for the utility of biochemical monitoring. In the present review, we have attempted to clarify the knowns and unknowns about treatment parameters in 21-OHD during childhood.

First Morning Pregnanetriol and 17-Hydroxyprogesterone Correlated Significantly in 21-Hydroxylase Deficiency

BACKGROUND

Biochemically monitoring 21-hydroxylase deficiency (21-OHD) is challenging. Serum/blood 17-hydroxyprogesterone (17OHP) measurements are normally used for this purpose. Urinary pregnanetriol (PT), a urinary metabolite of 17OHP, may also be used. Based on auxological data, we previously reported that the optimal first morning PT value fell in the range of 2.2-3.3 mg/gCr (95% confidence interval of the mean) and 0.59-6.0 mg/gCr (10^th - 90^th percentile) for monitoring 21-OHD treatment. No report thus far has directly compared the first morning urinary PT value with the 17OHP value at various times during the day.

OBJECTIVE

To explore the correlation between the first morning urinary PT value before glucocorticoid administration and the serum/blood 17OHP value at three time points, namely, before and two and four hours after glucocorticoid administration.

DESIGN

This was a prospective study done at two children's hospitals.

METHODS

In total, 25 patients with 21-OHD aged 3-25 years were recruited. Their urinary PT levels and 17OHP levels were measured for three days within a total period of one week. The first morning PT value was collected on all three days. Dried blood spots and serum were used to measure 17OHP.

RESULTS

The range for the first morning PT value for all the samples (n=69) was 0.10-56.1 mg/gCr. A significant, positive correlation was found between the first morning PT and 17OHP values before medication (r=0.87, p<0.01), and weaker correlation was observed between the first morning PT and 17OHP values after medication.

CONCLUSIONS

The first morning PT correlated more significantly with 17OHP before the morning medication. Measuring the first morning PT value may be more practical and useful for monitoring 21-OHD biochemically.

Therapy monitoring in congenital adrenal hyperplasia by dried blood samples

Careful monitoring of the therapy is crucial for patients with congenital adrenal hyperplasia (CAH) in order to prevent the effects of increased androgen production as well as life-threatening salt-wasting crisis. The key metabolite, 17α-hydroxyprogesterone (17-OHP) can be detected in serum, saliva or dried blood. In clinical practice there are challenges due to discomfort of venous blood sampling and complicated retrieval of saliva during infancy. Furthermore, the immunoassay method is limited in its specificity due to cross-reactions. In this observational study we prospectively examined over a period of 5 years, 20 patients with CAH due to 21-hydroxylase deficiency using standard immunoassays for serum samples (radioimmunoassay and enzyme immunoassay) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) in dried blood spots. Bland-Altman plots show goodness of agreement between both the methods for the desirable therapeutic concentration range of 17-OHP. LC-MS/MS is characterized by a high accuracy in the therapeutic concentration range of 17-OHP <100 nmol/L (r=0.91). Dried blood samples are convenient and reliable specimen for 17-OHP measured by LC-MS/MS. This method could be used for home monitoring of hydrocortisone replacement therapy both in salt-waster and simple virilizer CAH.

Congenital adrenal hyperplasia due to 21-hydroxylase deficiency

More than 90% of cases of congenital adrenal hyperplasia (CAH, the inherited inability to synthesize cortisol) are caused by 21-hydroxylase deficiency. Females with severe, classic 21-hydroxylase deficiency are exposed to excess androgens prenatally and are born with virilized external genitalia. Most patients cannot synthesize sufficient aldosterone to maintain sodium balance and may develop potentially fatal "salt wasting" crises if not treated. The disease is caused by mutations in the CYP21 gene encoding the steroid 21-hydroxylase enzyme. More than 90% of these mutations result from intergenic recombinations between CYP21 and the closely linked CYP21P pseudogene. Approximately 20% are gene deletions due to unequal crossing over during meiosis, whereas the remainder are gene conversions--transfers to CYP21 of deleterious mutations normally present in CYP21P. The degree to which each mutation compromises enzymatic activity is strongly correlated with the clinical severity of the disease in patients carrying it. Prenatal diagnosis by direct mutation detection permits prenatal treatment of affected females to minimize genital virilization. Neonatal screening by hormonal methods identifies affected children before salt wasting crises develop, reducing mortality from this condition. Glucocorticoid and mineralocorticoid replacement are the mainstays of treatment, but more rational dosing and additional therapies are being developed.

Correlation of blood-spot 17-hydroxyprogesterone daily profiles and urinary steroid profiles in congenital adrenal hyperplasia

OBJECTIVE

To compare the value of blood-spot 17-hydroxyprogesterone (17-OHP) daily profiles and urinary steroid excretion in untreated and treated patients with congenital adrenal hyperplasia (CAH).

PATIENTS

Ten patients with CAH were investigated during steroid replacement therapy (Group 1), and 11 patients were investigated without treatment (Group 2).

METHODS

Capillary blood samples were collected for measurement of blood-spot 17-OHP values by non-chromatographic radioimmunoassay. Steroid profiles of 24-h urine samples were analyzed by gas chromatography.

RESULTS

There was a close correlation between the individual daily means of blood-spot 17-OHP measurements and the pregnanetriol/ tetrahydrocortisone ratio in both groups of patients (Group 2: r=0.839, p<0.001; Group 1: r=0.686, p<0.001). Almost the same correlation was found between the blood-spot 17-OHP value and the sum of three 17-hydroxyprogesterone metabolites/the sum of three cortisol/cortisone metabolites ratio (Group 2: r=0.918, p<0.001; Group 1: r=0.741, p<0.001).

CONCLUSIONS

Blood-spot 17-OHP measurements and 24-h urinary steroid profile have the same impact in identification and monitoring therapy of children with CAH.

Development of a plasma 17alpha-hydroxyprogesterone time resolved-fluorescence immunoassay involving a new biotinylated tracer

A biotinylated 17alpha-hydroxyprogesterone probe (3) was prepared from 17alpha-hydroxyprogesterone-3-carboxymethyloxime and conjugate obtained by acylation of biotinylaminopropylammonium trifluroacetate. This new tracer was used in the development of a 17alpha-hydroxyprogesterone time-resolved fluoroimmunoassay using streptavidin-europium. The new method was compared to a long-standing radioimmunoassay method and found to be more sensitive and economical.

Loss of therapeutic control in congenital adrenal hyperplasia due to interaction between dexamethasone and primidone

A 14-year-old girl with congenital adrenal hyperplasia showed rapid conversion from undertreatment to overtreatment when primidone, used to treat coexistent epilepsy, was withdrawn while on a constant steroid dose. In addition to signs of hypercortisolism and a decrease in random measurements of plasma testosterone and 170H-progesterone concentrations, the deterioration in control was also illustrated by changes in the pattern of blood spot steroid profiles. Adequate control was achieved only after a 3-fold reduction in steroid dose. The decrease in dose requirement was probably the result of a reversal of liver enzyme induction consequent upon the withdrawal of primidone.

170H-progesterone rhythms in congenital adrenal hyperplasia

Serial blood spot and saliva samples were collected at home by 18 patients being treated for congenital adrenal hyperplasia to determine the circadian rhythm of 170H-progesterone as an index of therapeutic control. There was a strong correlation between the magnitude of the circadian fall and a single morning measurement of the plasma testosterone concentration taken near the time of the 170H-progesterone rhythm samples. Poor control in pubertal girls produced an exaggerated circadian fall in 170H-progesterone concentrations that were raised at all sampling times. Optimal control (plasma testosterone 1.5-2.5 nmol/l) was associated with blood spot and salivary 170H-progesterone concentrations at 0800 hours of between 30-70 nmol/l and 260-1000 pmol/l, respectively, falling thereafter to less than 10 nmol/l and less than 150 pmol/l, respectively. Similar results were obtained in prepubertal patients. Nomograms have been constructed to interpret the daily profiles of blood spot or salivary measurements of 170H-progesterone, or both. The analysis of 170H-progesterone circadian rhythms is useful in monitoring treatment in patients with congenital adrenal hyperplasia, particularly those who may be overtreated.

Blood spot glucocorticoid concentrations in ill preterm infants

The adrenocortical response to stress was studied longitudinally in 10 ill preterm infants using measurements of cortisol and 170H-progesterone concentrations in filter paper blood spots. Mean cortisol and 170H-progesterone concentrations reached a peak of 2200 nmol/l and 65 nmol/l, respectively, between the third and fifth days of life. These concentrations far exceeded those observed in older children and adults subjected to stress as a result of surgery. Further pulses of endogenous cortisol production of 4000 nmol/l or more occurred in association with clinical complications such as intraventricular haemorrhage. These results indicate that infants undergoing intensive care are unduly stressed. Consideration should be given to providing enough sedation and appropriate analgesia for ill preterm infants during painful procedures such as insertion of venous cannulae and arterial puncture.