Pediatric Adrenal Insufficiency: Challenges And Solutions Ⅱ

Genetic Disorders and Other Conditions at Increased Risk for Adrenal Insufficiency

Among the cholesterol biosynthesis disorders, there is the Smith-Lemli-Opitz syndrome,23 where microcephaly, micrognathia, low-set posteriorly rotated ears, syndactyly of the second and third toes, and atypical genital may, although rarely, combine with AI; this autosomal recessive disorder is due to defective 7-dehydrocholesterol reductase so that elevated 7-dehydrocholesterol is diagnostic. In lysosomal acid lipase A deficiency,24 AI is due to calcification of the adrenal gland as a result of the accumulation of esterified lipids; in infantle form, that is Wolman disease, hepatosplenomegaly with hepatic fibrosis and malabsorption lead to death in the first year of life, if not treated with enzyme replacement therapy such as sebelipase alfa.25

Adrenal development may be impaired in X-linked congenital adrenal hypoplasia (AHC),13,26 a disorder caused by defective nuclear receptor DAX-1, presenting with salt-losing AI in infancy in approximately half of the cases, but also later in childhood or adolescence with two other key features such as hypogonadotropic hypogonadism and impaired spermatogenesis. Two syndromes combine adrenal hypoplasia with intrauterine growth restriction (IUGR): in IMAGe syndrome,27 caused by CDKN1C gain-of-function mutations, IUGR and AI present with metaphyseal dysplasia and genitourinary anomalies; MIRAGE syndrome28 is instead characterized by myelodysplasia, infections, genital abnormalities, and enteropathy, as a result of gain-of-function mutations in SAMD9, with elevated mortality rates.

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In some other conditions, AI is due to ACTH resistance. Familial Glucocorticoid Deficiency type 1 (FGD1)13,29 and type 2 (FGD2)30 derive from defective ACTH receptor (MC2R) or its accessory protein MRAP, and both present with early glucocorticoid insufficiency (hypoglycemia, prolonged jaundice) and pronounced hyperpigmentation; there is usually an excellent response to cortisol replacement therapy, even though ACTH levels remain elevated.

In Allgrove or Triple-A Syndrome,13,31 defective Aladin protein (an acronym for alacrimia-achalasiaadrenal insufficiency) leads to primary ACTH-resistant adrenal insufficiency with achalasia and absent lacrimation, often combined with neurological dysfunction, either peripheral, central, or autonomic. It is an autosome recessive condition, phenotypically characterized by microcephaly, short stature, and skin hyperpigmentation.32,33

Among metabolic disorders associated with AI, Sphingosine-1-Phosphate Lyase (SGPL1) Deficiency34 is a sphingolipidosis with various features such as steroid-resistant nephrotic syndrome, primary hypothyroidism, undescended testes, neurological impairment, lymphopenia, ichthyosis; interestingly, in cases where nephrotic syndrome develops before AI, the latter may be masked by glucocorticoid treatment.

Adrenoleukodystrophy (ALD)35–37 is an X-linked recessive proximal disorder of beta-oxidation due to defective ABCD1, where the accumulation of very-long-chain fatty acids (VLCFA) affects in almost all cases adrenal gland among other tissues. Most patients present with progressive neurological impairment, but in some, AI is the only (approximately 10%) or first manifestation, so every unexplained AI in boys should receive plasma VLCFA evaluation to diagnose ALD and reduce cerebral involvement through a low VLCFAs diet (Lorenzo's oil) and allogeneic bone marrow transplantation. Early disease-modifying therapies have been developed. Gene therapy adds new functional copies of the ABCD1 gene in hematopoietic stem cells through a lentiviral vector reinfusing the modified cells in the patient's bloodstream. Recent trials show encouraging results.38

In Zellweger syndrome, caused by mutations in peroxin genes (PEX), peroxisomes are absent, and disease presentation occurs in the neonatal period, with low survival rates after the first year of life. Finally, mitochondrial disorders have been described to occasionally develop AI: Pearson syndrome (sideroblastic anemia, pancreatic dysfunction), MELAS syndrome (encephalopathy with stroke-like episodes), and Kearns-Sayre syndrome (external ophthalmoplegia, heart block, retinal pigmentary changes) belong to this class.39

Autoimmune pathogenesis (Addison disease) accounts for approximately 15% of cases of primary AI in children, in contrast with adolescents and adults where it is the most common mechanism; half of these children present other glands involvement as well. Two syndromes recognize specific combinations: in Autoimmune Polyglandular Syndrome Type 1 (APS1, or APECED)40 defective autoimmune regulator AIRE causes AI, hypoparathyroidism, hypogonadism, malabsorption, chronic mucocutaneous candidiasis; APS2 usually present later in life (thirdfourth decades) with AI, thyroiditis, and type 1 diabetes mellitus (T1DM). Antibodies against 21-hydroxylase enzyme are the hallmark of APS.

Apart from a genetic disorder, a strong link between autoimmune conditions and autoimmune primary AI has been established, with more than 50% of patients with the latter also having one or more other autoimmune endocrine disorders; on the other hand, only a few patients with T1DM or autoimmune thyroiditis or Graves' disease develop AI. As an example, in a study of 629 patients with T1DM, only 11 (1.7%) presented 21-hydroxylase autoantibodies, with three of them having AI.41 Nevertheless, these patients are to be considered at increased risk for a condition that is potentially fatal yet easy to diagnose and treat; that is why it is reasonable to screen for autoimmune AI at least patients with T1DM, significantly if associated with DQ8 HLA combined with DRB*0404 HLA alleles, who have been observed to develop AI in 80% of cases if also 21- hydroxylase autoantibodies positive.42

Regarding immunological disruption, the link with celiac disease is instead well established: celiac patients have an 11-fold increased risk for AI, while in a study, 6 of 76 patients with AI had celiac disease, so that mutual evaluation should be granted in these patients.43,44

Subclinical Adrenal Insufficiency 

Subclinical AI is a particularly insidious challenge for a pediatric endocrinologist. It represents the preclinical stage of Addison disease when 21-hydroxylase autoantibodies are already detectable but still absent from evident symptoms. 21-hydroxylase autoantibodies positivity carries a greater risk of developing overt AI in children than in adults: in a study, the estimated risk was 100% in children versus 32% in adults on a medium six-year period of follow-up.45 As the adrenal crisis is a potentially lethal condition, it is essential to recognize and adequately manage subclinical AI.

Although asymptomatic by definition, subclinical AI may present with non-specific symptoms such as fatigue, lethargy, gastrointestinal symptoms (nausea, vomiting, diarrhea, constipation), and hypotension; physical or psycho-social stresses may sometimes exacerbate these symptoms. When symptoms lack, subclinical AI may be identified thanks to the co-occurrence with other autoimmune endocrinopathies.46

21-hydroxylase autoantibody titer is considered a marker of autoimmune activity and correlates with disease progression.47 Other reported risk factors for the disease evolution include young age, male sex, hypopar athyroidism or candidiasis coexistence, increased renin activity, or an altered synacthen test with normal baseline cortisol and ACTH.45 ACTH elevation has been reported as the best predictor of progression to the clinical stage in 2 years (94% sensitivity and 78% specificity).48

Management of patients with subclinical AI should include serum cortisol, ACTH, renin measurement, and a synacthen test. If normal, cortisol and ACTH should be repeated in 12–18 months, while synacthen test every two years. After synacthen test results are subnormal, cortisol and ACTH should be assessed every 6–9 months if ACTH remains in range or every six months if ACTH becomes elevated.49 In the latter case, therapy with hydrocortisone should be started.19 This strategy will prevent acute crises and possibly improve the quality of life in patients reporting non-specific symptoms.

Diagnosis

Laboratory evaluation of a stable patient with suspected AI should start with combined early morning (between 6 and 8 AM) serum cortisol and ACTH measurements (Figure 2)

Figure 2 Diagnostic algorithm for adrenal insufficiency

Although often included in the extensive work-up of an unwell child, a single cortisol value is usually challenging to interpret: circadian cortisol rhythm is highly variable and morning peak is unpredictable; morning cortisol levels in children with diagnosed AI may range up to 706 nmol/L (97th percentile); several factors, such as exogenous estrogens, may alter total serum cortisol values by influencing the free cortisol to cortisol binding globulin or albumin-bound cortisol ratio.7

Significant variability is also observed depending on the specific type of cortisol assay; therefore, it is recommended to check the reference ranges with the laboratory. Mass spectrometry analysis and the new platform methods (Roche Diagnostics Elecsys Cortisol II)50 have more specificity because it detect lower cortisol concentrations than standard immunoassays.15 Low serum cortisol with normal or low ACTH levels is compatible with CAI. In such cases, morning serum cortisol levels below 3 µg/dL (83 nmol/L) best predict AI, while greater than 13 µg/dL (365 nmol/L) values tend to exclude it.51 This is why in most cases, a dynamic test is required for diagnosis and has been introduced to assess the hypothalamic-pituitary-adrenal (HPA) axis in case of intermediate values.5

The insulin tolerance test (ITT) is considered the gold standard for CAI diagnosis as hypoglycemia results in an excellent HPA axis activation; moreover, it allows simultaneous growth hormone evaluation in patients with suspected CPHD. Serum cortisol is measured at baseline and 15, 30, 45, 60, 90, and 120 minutes after intravenous administration of 0.1 UI/Kg regular insulin; the test is valid if serum glucose is reduced by 50% or below 2.2 mmol/L (40 mg/dL).52 CAI is diagnosed for a <20 µg/dL (550 nmol/L) cortisol value at its peak.15 Hypoglycemic seizures and hypokalemia (due to glucose infusion) are the main risks of this test so it is contraindicated in case of a history of seizures or cardiovascular disease.

Glucagon stimulation test (GST, 30 µg/Kg up to 1 mg i.m. glucagon with cortisol measurements every 30 min for 180 min) allows both CAI and growth hormone deficiency evaluation as well but is characterized by frequent gastrointestinal side effects and poor specificity.8

Metyrapone is an 11-hydroxylase inhibitor, thereby decreasing cortisol synthesis and removing its negative feedback on ACTH release. The overnight metyrapone test is based on oral administration of 30 mg/Kg metyrapone at midnight, and 11-deoxycortisol measurement on the following morning: in case of CAI, its level will not reach 7 µg/dL (200 nmol/L). This test may, however, induce an adrenal crisis so that it is rarely performed.

Given their safety profile and accuracy, corticotropin analogs such as tetracosactrin (Synacthen®) or cosyntropin (Cortrosyn®) are recommended as first-line stimulation tests. Nevertheless, false-negative results are probable in the case of recent or moderate ACTH deficiency, which would not have induced adrenal atrophy. The standard dose short synacthen test (SDSST) is based on a 250 µg Synacthen vial administration with serum cortisol measurement at baseline and 30 and 60 minutes after. CAI is diagnosed if peak cortisol level is <16 µg/dL (440 nmol/ L), or excluded if >39 µg/dL (1076 nmol/L). However, the cut-offs for both the new platform immunoassay and mass spectrometry serum cortisol assays are 13.5 to 14.9 mcg/ dL (373 to 412 nmol/L).53 The 250 µg Synacthen dose is considered a supraphysiological stimulus since it is 500 times greater than the minimum ACTH dose reported to induce a maximal cortisol response (500 ng/1.73 m2 ). The low-dose short synacthen test (LDSST) has been introduced as a more sensitive first-line test in children greater than two years.54 The recommended dose is 1 µg55, which is contained in 1 mL of the solution obtained by diluting a 250 µg vial into 250 mL saline. Serum cortisol level is then measured at baseline and after 30 minutes, resulting in diagnosis of CAI if <16 µg/dL (440 nmol/L), otherwise ruling it out if >22 µg/dL (660 nmol/L). Using these thresholds, LDSST is more precise than SDSST in children, with an area under the ROC curve of 0.99 (95% CI 0.98–1.00).56 LDSST has not been validated in acutely ill patients, pituitary acute disorders or surgery or radiation therapy, and impaired sleep-wake cycle. Patients with an indeterminate LDSST result should be further studied with ITT or metyrapone test.

Finally, the CRH test is based on 1 µg/Kg human CRH (Ferring®) administration and may differentiate secondary from tertiary AI, but its thresholds are still not precisely defined.57

Once CAI is diagnosed, other pituitary hormones should be assessed (prolactin, IGF1, LH, FSH, fT4, TSH), and an MRI of the pituitary region should be performed to exclude neoplastic or infiltrative processes.

Primary adrenal insufficiency (PAI) should be suspected in case of low serum cortisol with elevated ACTH levels. When hypocortisolemia has been confirmed, ACTH levels >66 pmol/L or greater than twice the upper limit best predict PAI. Nevertheless, a confirmatory dynamic test is always recommended for diagnosis.19 Given the comparable accuracy between standard and low-dose SST reported in these patients, SDSST is recommended as the most feasible test.58 Moreover, suspected PAI cases should receive plasma renin activity or direct renin and aldosterone assessment to evaluate mineralocorticoid deficiency.

Etiologic work-up of confirmed PAI should start from 21-hydroxylase antibodies assessment: if positive, differential diagnosis will include Addison disease and APS1 or APS2. Adrenal autoantibody-negative patients should instead be screened for CAH by measuring 17- hydroxyprogesterone, ALD (if young male) by assessing VLCFA, and tuberculosis if endemic; adrenal glands imaging will complete the work-up in order to exclude infection, hemorrhage, or tumor.6

While universal newborn screening is already implemented for CAH in many countries, allowing a timely replacement therapy, basal salivary cortisol, and salivary cortisone measurements could improve CAI screening in the future: this technique is simple, cost-effective, and independent of binding proteins.15

Treatment 

All patients with adrenal insufficiency need long-term glucocorticoid replacement therapy. Individuals with PAI also require mineralocorticoid replacement, together with salt intake as required (Table 4). Otherwise, guidelines do not recommend androgen replacement.5,9,19

Oral hydrocortisone is the first-choice replacement treatment in children due to its short half-life, rapid peak in plasma concentration, lower potency, and fewer adverse effects than prednisolone and dexamethasone.5,8 Based on endogenous production, dosing replacement regimens vary from 7.5 to 15 mg/m2/day, divided into two, three, or four doses.19 The first and largest dose should be taken at awakening, the next in the early afternoon to avoid sleep disturbances. Small and frequent dosing mimic the physiological rhythm of cortisol secretion, but high peak cortisol levels after drug assumption and prolonged periods of hypocortisolemia between doses are described.8,9 Some children experience low cortisol concentrations and symptoms of cortisol insufficiency (eg, fatigue, nausea, headache) despite modifications in dosing. This cohort of patients can take advantage of using a modified-release hydrocortisone formulation, such as Chronocort® and Plenadren®. Plenadren®, approved for adults, consists of a coating of hydrocortisone released rapidly, followed by a slow release of hydrocortisone from the tablet center. It is available as 5 and 20 mg tablets. Park et al demonstrate smoother cortisol profiles and normal growth and weight gain patterns using Plenadren® in children.59 In a few cases, the continuous subcutaneous infusion of hydrocortisone using insulin pump technology proved to be a feasible, well-tolerated and safe option for selected patients with poor response to conventional therapy.19

Monitoring glucocorticoid therapy is based on growth, weight gain, and well-being. Cortisol measurements are usually not useful, apart from cases when a discrepancy between daily doses and patient symptoms exists.15 The concomitant use of hydrocortisone and CYP3A4 inducers, such as Rifampicin, Phenytoin, Carbamazepine, requires an increased dose of glucocorticoids. Conversely, the inhibition of CYP3A4 impairs hydrocortisone metabolism.5

Mineralocorticoid replacement is unnecessary if the patient has a normal renin-angiotensin-aldosterone axis and, hence, normal aldosterone secretion, as well as in CAI. By contrast, patients with PAI and confirmed aldosterone deficiency need fludrocortisone at the dosage of 0.1–0.2 mg/day when given together with hydrocortisone, which has some mineralocorticoid activity. When using other synthetic glucocorticoids for replacement, higher fludrocortisone doses may be needed. Infants younger than one year should also be supplemented with sodium chloride due to their relatively low dietary sodium intake and relative renal resistance to mineralocorticoids. The dose is approximately 1 gram (17 mEq) daily.19

Surgery and anesthesia increase the glucocorticoid requirement during the pre-, intra-, and post-operative periods (Table 4). All children with AI should receive an intravenous dose of hydrocortisone at induction (2 mg/kg for minor or major surgery under general anesthesia). For minor procedures or sedation, the child should receive a double morning dose of hydrocortisone orally.60

Adrenal crisis is a life-threatening condition, treatment is effective if administered promptly, and it must not be delayed for any reason. Hydrocortisone should be administered as soon as possible with an intravenous bolus of 4 mg/kg followed by a continuous infusion of 2 mg/kg/day until stabilization. In the alternative, it can be administered as a bolus every four hours intravenous or intramuscular. In difficult peripheral venous access, the intramuscular route must be used as the first choice. In order to counteract hypotension, a bolus of normal saline 0.9% should be given at a dose of 20 mL/kg; it can repeat up to a total of 60 mL/kg within one hour for shock. If there is hypoglycemia, 10% dextrose at a 5 mL/kg dose should be administered.5,19,61,62

Patients with AI require additional doses of glucocorticoids in case of physiologic stress such as illness or surgical procedures to avoid an adrenal crisis. Home management of illness with a fever (> 38°C), vomiting or diarrhea, is based on the increase from two to three times the usual dose orally. If the child is unable to tolerate oral therapy, intramuscular injection of hydrocortisone should be administered (Table 4).

Education for caregivers and patients (if adolescent) is crucial to prevent adrenal crisis. They should recognize signs and symptoms of adrenal crisis and should receive a steroid emergency card with the sick day rules. Prescribing doctors should provide for additional oral glucocorticoids and adequate training in hydrocortisone emergency self-injection.

References

1. Charmandari E, Nicolaides N, Chrousos G. Adrenal insufficiency. Lancet. 2021;383(9935):2152–2167. doi:10.1016/S0140-6736(13) 61684-0 

2. White PC. Adrenocortical insufficiency. In: Nelson Textbook of Pediatrics. Elsevier. 2019:11575–11617. 

3. White PC. Physiology of the adrenal gland. Nelson Textbook of Pediatrics. Elsevier. 2019. 

4. Butler G, Kirk J. Adrenal gland disorders. In: Paediatric Endocrinology and Diabetes. Oxford University Press. 2020:274–288. 

5. Patti G, Guzzeti C, Di Iorgi N, Loche S. Central adrenal insufficiency in children and adolescents. Best Pract Res Clin Endocrinol Metab. 2018;32(4):425–444. doi:10.1016/j. beem.2018.03.012

6. Martin-grace J, Dineen R, Sherlock M, Thompson CJ. Adrenal insufficiency: physiology, clinical presentation and diagnostic challenges. Clin Chim Acta. 2020;505:78–91. doi:10.1016/j.cca.2020.01.029 

7. Shaunak M, Blair JC, Davies JH. How to interpret a single cortisol measurement. Arch Dis Child Educ Pract. 2020;105:347–351. doi:10.1136/archdischild-2019-318431 

8. Park J, Didi M, Blair J. The diagnosis and treatment of adrenal insuf fi ciency during childhood and adolescence. Arch Dis Child. 2016;101:860–865. doi:10.1136/archdischild-2015-308799 

9. Husebye ES, Pearce SH, Krone NP, Kämpe O. Adrenal insufficiency. Lancet. 2021;397:613–629. doi:10.1016/S0140-6736(21)00136-7 

10. Speiser P, Azziz R, Baskin L, et al. Congenital adrenal hyperplasia due to steroid 21-hydroxylase deficiency: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2010;95 (9):4133–4160. doi:10.1210/jc.2009-2631

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