Idiopathic short stature is not a diagnosis: A strategy is needed to identify the true pathogenesis in cases of unexplained short stature
The designation “Idiopathic short stature” (ISS) was first used in the 1980s as a description for short children who had normal growth hormone (GH) secretion and otherwise unexplained short stature. ISS acquired clinical significance following the introduction of recombinant human (h)GH in 1985 and the approval of GH deficiency (GHD) by the FDA and EMA for hGH replacement therapy. Trials of hGH in ISS subjects were started, guided by collaborations between pharma companies and academic institutions, because patients with the ISS label were shown to have comparable degrees of short stature to GHD patients.
These short children therefore deserved an opportunity to possibly benefit from hGH prescribed in a higher pharmacological dose. Positive data demonstrated efficacy of hGH in the ISS subjects in randomised placebo-controlled trials. Although the growth responses were highly variable, highlighting the heterogeneous nature of these patients, the overall positive responses and absence of safety signals led to successful applications to the FDA and, in 2003, ISS became an approved indication for hGH therapy. Similar applications by pharma companies to the EMA were rejected, largely due to the absence of improvement in quality of life variables. Consequently, ISS is not a reimbursable condition in countries not covered by FDA jurisdictions.
Since the emergence of molecular biological investigation of patients with growth disorders, which started in the late 1980s and accelerated considerably in the 1990s and through to the 21st century, genetic defects have repeatedly been discovered in children previously labelled as having ISS. Initial genetic studies were mainly in the GH–insulin-like growth factor (IGF)-1 axis, where defects in pituitary development and in genes coding for functional proteins in the pathway of GH action were identified. Examples are monogenic defects in the following genes: GH receptor (GHR); STAT5B; IGF1; IGFALS; IGF1R and PAPPA2 (2). However, recent attention has focused on genes involved in chondrogenesis and growth plate function as a key mechanism regulating normal linear growth (3). Genetic defects in the following growth plate genes have been identified in children carrying the label of ISS: SHOX; ACAN; NPR2; IHH; FGFR3.
In view of these recent discoveries, patients labelled as ISS deserve further investigation in an attempt to define their true pathogenesis. “ISS” is not a diagnosis, but a statement of diagnostic uncertainty. It is now clear that the three disciplines of diagnostic assessment, namely clinical evaluation, endocrine characterisation and genetic investigation, need to have equal status in the hierarchy of the short stature protocol (Figure 1). Clinical assessment is of crucial importance with essential documentation of family history, parental, grandparental and sibling height data, dysmorphology and body disproportion examination, in addition to developmental, feeding and behavioural milestones (4). General paediatric disorders, such as celiac disease and Turner syndrome need to be excluded. Endocrine evaluation should document GH and IGF-1 status. Genetic investigations should centre around the search for monogenic defects with major growth effects, rather than polygenic defects with multiple minor effects.
A working relationship should be established between the clinician and a molecular biologist for discussion of which short patients should undergo genetic tests, which are the appropriate techniques to use and how can the results of the tests be best interpreted. Such a relationship will bring considerable dividends in terms of academic learning, patient care and research opportunities. For example, candidate gene sequencing, indicated when a phenotype suggests a specific genetic diagnosis, is largely being replaced by the hypothesis-free approach of whole-exome sequencing using specific gene panels, which have given diagnostic yields in ~35% of unexplained short stature patients in some reports (5).
ISS is a convenient term for patients with unexplained short stature and is likely to remain in clinical usage. The scheme proposed in Figure 1 gives equality to the three diagnostic disciplines of clinical, endocrine and genetic studies to pursue the primary cause of short stature in unexplained cases. This approach has the realistic chance of clarifying the molecular pathogenesis of known or novel growth disorders. By explaining the basic mechanistic defects, genetic results can guide therapy and thereby enhance progression to optimisation of clinical management.
1. Baron J, Sävendahl L, De Luca F, Dauber A, Phillip M, et al. Short and tall stature: a new paradigm emerges. Nat Rev Endocrinol 2015; 11: 735–746. doi: 10.1038/nrendo.2015.165.
2. Cohen P, Rogol AD, Deal CL, Saenger P, Reiter EO, et al. Consensus statement on the diagnosis and treatment of children with idiopathic short stature: a summary of the Growth Hormone Research Society, the Lawson Wilkins Pediatric Endocrine Society, and the European Society for Paediatric Endocrinology Workshop. J Clin Endocrinol Metab 2008; 93: 4210–4217. doi: 10.1210/jc.2008-0509
3. Storr HL, Chatterjee S, Metherell LA, Foley C, Rosenfeld RG, et al. Nonclassical GH Insensitivity: Characterization of Mild Abnormalities of GH Action. Endocr Rev 2019; 40: 476–505. doi: 10.1210/er.2018-00146.
4. Wit JM, Kamp GA, Oostdijk W. on behalf of the Dutch Working Group on Triage and Diagnosis of Growth Disorders in Children. Towards a Rational and Efficient Diagnostic Approach in Children Referred for Growth Failure to the General Paediatrician. Horm Res Paediatr 2019; 91: 223–240 doi: 10.1159/000499915.
5. Hauer NN, Popp B, Schoeller E, Schuhmann S, Heath KE, et al. Clinical relevance of systematic phenotyping and exome sequencing in patients with short stature. Genet Med 2018; 20: 630–638. doi: 10.1038/gim.2017.159.
Supporting families of paediatric patients with adrenal disease
While adrenal disease in children is quite rare (Simpson et al., 2018), healthcare professionals today working in paediatric endocrinology departments are experts in managing the care of children with adrenal disease. Congenital adrenal hyperplasia (CAH) is the most common; primary adrenal insufficiency and Cushing’s syndrome are also rare but important disorders.
It is useful for families to learn more detail on what is involved in CAH from this helpful video from the patient support group “Living with CAH.”
It is very important that the prescribed medications are taken correctly and on time, as children may have a life-threatening adrenal crisis if they do not have enough of the hormone cortisol in their system (Miller et al., 2020). Babies will have to take extra liquid salt supplements every day until they are fully weaned (Padidela & Hindmarsh, 2010), and it is important that parents know the correct pharmacy to obtain this from. Fludrocortisone tablets are given to treat reduced levels of aldosterone, and hydrocortisone replacement is also needed for basic cortisol replacement, given at different times throughout the day. The tablets can be crushed and mixed with water to obtain the correct dose, which can be quite small in children (Watson et al., 2018), or there is a paediatric-specific formulation, which comes as capsules that can be broken open and the small grains administered (Porter, Withe, & Ross, 2018).
When children are unwell, hydrocortisone doses will need to be doubled or trebled until clinical improvement occurs. In an emergency, an injection of hydrocortisone needs to be administered, and the PENS can help train the family for this eventuality. A useful app (Tollerfield, Atterbury, Langham, Morris, & Farrell, 2017) formulated by the team at Great Ormond Street Hospital also demonstrates the injection (see image), and the team have other useful information at the following links:
Education in the primary disorder will underpin the understanding of families to have a full stock of the medication at home. The PENS can help liaise with nurseries and schools and agree on a management plan regarding medication and potential emergency scenarios. A steroid therapy card should always be with the child and the PENS can formulate hand-held emergency management plans to be kept at school, with both parents, at grandparents’ houses etc. Medic alert bracelets are also advised to be worn at all times.
Travel advice can also be given by the PENS, focusing on when to take the medication across different time zones, advice for travelling with an emergency kit on an aeroplane, emergency plans in relevant languages, and possibly the contact details of the local paediatric endocrine team (Moloney, Murphy, & Collin, 2015).
It is vital that families and healthcare professionals from a multidisciplinary team work together: the diagnosis can be alarming, but support from other families and support groups can be invaluable (Moloney et al., 2015), with education being the key to optimum and safe management (Bowden & Henry, 2018).
Bowden, S. A., & Henry, R. (2018). Pediatric Adrenal Insufficiency: Diagnosis, Management, and New Therapies. Int J Pediatr 2018; 1739831. doi:10.1155/2018/1739831
Miller, B. S., Spencer, S. P., Geffner, M. E., Gourgari, E., Lahoti, A., Kamboj, M. K., Sarafoglou, K. Emergency management of adrenal insufficiency in children: advocating for treatment options in outpatient and field settings. J Investig Med 2020; 68: 16–25. doi:10.1136/jim-2019-000999
Moloney, S., Murphy, N., & Collin, J. An overview of the nursing issues involved in caring for a child with adrenal insufficiency. Nurs Child Young People 2015; 27; 28–36. doi:10.7748/ncyp.27.7.28.e609
Padidela, R., & Hindmarsh, P. C. Mineralocorticoid deficiency and treatment in congenital adrenal hyperplasia. Int J Pediatr Endocrinol 2010; 656925. doi:10.1155/2010/656925
Porter, J., Withe, M., & Ross, R. J. Immediate-release granule formulation of hydrocortisone, Alkindi(R), for treatment of paediatric adrenal insufficiency (Infacort development programme). Expert Rev Endocrinol Metab 2018; 13: 119–124. doi:10.1080/17446651.2018.1455496
Simpson, A., Ross, R., Porter, J., Dixon, S., Whitaker, M. J., & Hunter, A. Adrenal Insufficiency in Young Children: a Mixed Methods Study of Parents’ Experiences. J Genet Couns 2018; 27: 1447–1458. doi:10.1007/s10897-018-0278-9
Tollerfield, S., Atterbury, A., Langham, S., Morris, S., & Farrell, N. C1.4 My cortisol, development of a life saving app. Arch Dis Child 2017; 102; A5. doi:10.1136/archdischild-2017-084620.12
Watson, C., Webb, E. A., Kerr, S., Davies, J. H., Stirling, H., & Batchelor, H. How close is the dose? Manipulation of 10mg hydrocortisone tablets to provide appropriate doses to children. Int J Pharm 2018; 545: 57–63. doi:10.1016/j.ijpharm.2018.04.054
Professor Ieuan Hughes and Dr Rieko Tadokoro-Cuccaro
Medical management of congenital adrenal hyperplasia: can conventional therapy be replaced by novel treatments?
Congenital adrenal hyperplasia (CAH) is a disorder of decreased cortisol production coupled with an increase in androgens from a compensatory adrenocorticotropic hormone (ACTH) drive. Glucocorticoid and mineralocorticoid replacement is the standard treatment for CAH. The optimal goal is to ensure well-being, prevent adrenal crises and suppress excess androgens but this is unrealistic using conventional treatment. The price paid is childhood growth suppression and adult morbidity associated with obesity and cardiovascular disease. How can this conundrum be solved?
Immediate-release HC granules, Alkindi (Diurnal Ltd, UK), were developed for infants and children (1). They provide small dosing, flexibility and easy administration. Pharmacokinetic studies showed bioequivalence of Alkindi to the HC tablet.
Two modified-release HC preparations are in clinical trials to try to match endogenous cortisol rhythm: Plenadren (immediate and delayed release; Shire Pharmaceuticals Ltd, UK) and Chronocort (delayed and prolonged release; Diurnal Ltd, UK). A morning dose of Plenadren in 16 healthy adults produced a similar cortisol exposure to three times daily HC, except later in the day (2). A supplementary dose of HC would still be needed.
Chronocort was designed to mimic increasing cortisol levels overnight, peaking on awakening and falling to a nadir later in the day. Chronocort is taken twice daily in “toothbrush” mode at bedtime and on awakening. A phase 2 study in 16 adults with CAH showed profiles similar to endogenous cortisol; this resulted in reduced conventional HC doses and decreased androgens (3). A larger phase 3 study in 122 patients failed to confirm superiority over conventional treatment but the manufacturers of this agent have nevertheless been given permission to apply for EMA marketing authorization.
As an alternative to suppressing ACTH-induced androgens with modified HC, why not use a top-down approach to block ACTH? (Figure). The hypothalamic–pituitary–adrenal (HPA) axis is orchestrated by corticotrophin-releasing hormone or factor (CRH or CRF). Consequently, blocking this factor or the receptor to which it binds on the cell membrane of pituitary corticotroph cells would inhibit ACTH synthesis and reduce adrenal steroid production. A CRF1 receptor antagonist was studied in eight women with CAH in a phase 1b clinical trial (4), where a bedtime dose significantly reduced morning ACTH levels in a dose-dependent manner. In turn, this decreased concentrations of precursor steroids such as 17OH-progesterone and induced a reduction of androgens. Further studies of a novel approach to medical adrenalectomy are required but the results are promising.
Perhaps a complete shutdown of adrenocortical function can be achieved safely and replacement doses of HC and a mineralocorticoid added. This form of block and replace regimen would be akin to the non-surgical treatment of hyperthyroidism.
Other examples of non-conventional treatments for CAH include inhibiting the enzyme for adrenal androgen biosynthesis with abiraterone (5), blocking the action of androgens and oestrogens with steroid receptor antagonists (6), continuous infusion of HC by pump therapy similar to that used to treat insulin-dependent diabetes (7) and bilateral adrenalectomy (8). Such therapies have merit at an individual level, but are not suited for routine management of CAH.
Use of HC granules sprinkled on soft food is a practical step forward for infants and young children with CAH. Attempts to deliver HC to replicate endogenous cortisol secretion are progressing with some success. The more radical option of a neuroendocrine approach to the HPA axis by blocking CRH action also has exciting potential for the future medical management of CAH.
Support from the National Institute for Health Research Cambridge Biomedical Centre. R T-C is supported by the Cambridge Children’s Kidney Research Fund.
- Neumann U, Whitaker MJ, Wiegand S, et al. Absorption and tolerability of taste-masked hydrocortisone granules in neonates, infants and children under 6 years of age with adrenal insufficiency. Clin Endocrinol 2018; doi:10.1111/cen.13447
- Johannsson G, Bergthorsdottir R, Nilsson AG, et al.Improving glucocorticoid replacement therapy using a novel modified-release hydrocortisone tablet: a pharmacokinetic study. Eur J Endocrinol 2009; doi: 10.1530/EJE-09-0170
- Mallappa A, Sinaii N, Kumar P, et al. A phase 2 study of Chronocort, a modified-release formulation of hydrocortisone, in the treatment of adults with classic congenital adrenal hyperplasia. J Clin Endocrinol Metab 2015; doi:10.1210/jc.2014-3809
- Turcu AF, Spencer-Segal JL, Farber RH, et al. Single-dose study of a corticotropin-releasing factor receptor-1 antagonist in women with 21-hydroxylase deficiency. J Clin Endocrinol Metab; doi:10.1210/jc.2015-3574
- Auchus RJ, Buschur EO, Chang AY, et al.Abiraterone acetate to lower androgens in women with classic 21-hydroxylase deficiency. J Clin Endocrinol Metab 2014; doi:10.1210/jc.2014-1258
- Auchus RJ.Management considerations for the adult with congenital adrenal hyperplasia. Mol Cell Endocrinol 2015; doi:10.1016/j.mce.2015.01.039
- Nella AA, Mallappa A, Perritt AF, et al. A phase 2 Study of continuous subcutaneous hydrocortisone infusion in adults with congenital adrenal hyperplasia. J Clin Endocrinol Metab 2016; doi: 10.1210/jc.2016-1916
- MacKay D, Nordenström A, Falhammar H. Bilateral adrenalectomy in congenital adrenal hyperplasia: A systematic review and meta-analysis. J Clin Endocrinol Metab 2018; doi: 10.1210/jc.2018-00217
Noonan syndrome (NS) is a relatively common autosomal dominant disorder (1:1000 to 1:2500 live births) characterised by facial dysmorphism, short stature, chest deformities and congenital heart defects. Variable developmental delay and intellectual disability are also observed in some patients.
Disease-causing mutations in genes of the RAS/MAPK pathway are identified in 70–80% of affected patients (1). PTPN11 (protein tyrosine phosphatase, nonreceptor type 11) gene was the first causative gene identified in this condition and encodes a tyrosine phosphatase protein. Nearly 40–50% of patients with NS harbour heterozygous pathogenic variants in this gene.
The diagnosis of NS is based on classical clinic features and can be confirmed by the identification of a heterozygous pathogenic variant in one of the causative genes.
Currently, the diagnosis has been established mainly by multigene sequencing analysis (whole exome or target panel sequencing).
rhGH has been shown to be safe for patients with NS, mainly based on data from retrospective studies with a limited number of patients (3). For this reason, some concerns still remain about an increase in cancer risk and worsening of hypertrophic myocardiopathy in patients with NS treated with rhGH (4). Patients with specific mutations in PTPN11, KRAS and RIT1 can have a high rate of myeloproliferative disorder during the first 5 years of life. In those patients with genetic variants highly associated with myeloproliferative disorders, the decision to start rhGH therapy should be carefully discussed and only begun after the age of 5 years. Future studies are necessary to better define the impact of specific genotypes on growth response and safety of patients with NS treated with rhGH. However, some insights are already possible by identifying the molecular basis of a patient with NS.
- Tajan M, Paccoud R, Branka S, et al. The RASopathy Family: Consequences of Germline Activation of the RAS/MAPK Pathway. Endocr Rev doi: 10.1210/er.2017-00232
- Malaquias AC, Brasil AS, Pereira AC, et al. Growth standards of patients with Noonan and Noonan-like syndromes with mutations in the RAS/MAPK pathway. Am J Med Genet A 2012; doi: 10.1002/ajmg/a/35519
- Noonan JA, Kappelgaard AM. The efficacy and safety of growth hormone therapy in children with noonan syndrome: a review of the evidence. Horm Res Paediatr 2015; doi: 10.1159/000369012
- Malaquias AC, Noronha RM, Souza TTO, et al. Impact of Growth Hormone Therapy on Adult Height in Patients with PTPN11 Mutations Related to Noonan Syndrome. Horm Res Paediatr 2019: doi: 10.1159/000500264
- US Food & Drug Administration. Somatropin Information, as of 23 July 2015. https://www.fda.gov/drugs/postmarket-drug-safety-information-patients-and-providers/somatropin-information
- Binder G, Wittekindt N, Ranke MB. Noonan Syndrome: Genetics and Responsiveness to Growth Hormone Therapy. Horm Res Paediatr 2007; doi: 10.1159/000097552
Delayed puberty (DP) is common in the developed world, affecting over 2% of adolescents, and is associated with adverse health outcomes including short stature, reduced bone mineral density and compromised psychosocial health. The majority of patients have constitutional or self-limited DP, which is often familial, most commonly segregating in an autosomal dominant pattern. However, the key genetic regulators in self-limited DP are largely unknown , Figure 1.
Figure 1 – Schematic representing the genes (encircled) known to be involved in the pathogenesis of self-limited DP, and their overlap with cHH and loci identified by genome-wide association studies of age of puberty in the general population. Important genes identified in precocious puberty (DLK1 and MKRN3) and the Kisspeptin gene (KISS1) and its receptor (KISS1R) are also included.
Ieuan Hughes, MD FRCP FRCPCH FMedSci
Congenital adrenal hyperplasia: optimising cardiometabolic outcomes
The introduction of glucocorticoid replacement for congenital adrenal hyperplasia (CAH) has revolutionised the outlook for patients with this lifelong condition, preventing life-threatening salt-wasting crises. However, accumulating evidence shows persistently increased morbidity, and even mortality, in CAH patients, and links it not only to the disease, but also to the treatment.
Here we review key publications, selected by Ieuan Hughes, Emeritus Professor of Paediatrics from Addenbrooke’s Hospital in Cambridge, UK, which summarise the current knowledge and show how clinicians and the pharmaceutical industry are beginning to respond to this challenge.
For patients with the salt-wasting (classical) form of CAH, the introduction of glucocorticoid treatment in the 1950s turned the condition into a chronic illness, rather than a guarantee of early death.
And Hughes says that CAH was initially viewed as simple to treat: “Take your hydrocortisone, go away, no problem.”
Yet a 2014 Swedish registry study showed that the problem of salt-wasting crises was reduced, rather than entirely vanquished.1 The mortality rate was 3.9% among 588 CAH patients, compared with 1.6% among nearly 59,000 controls, and 42% of the deaths in CAH patients were due to adrenal crises. Other causes of death were cardiovascular, cancer, accident and suicide, and occurred at a similar rate as in controls. However, study authors Henrik Falhammar (Karolinska University Hospital, Stockholm, Sweden) and colleagues noted that half the cardiovascular deaths in CAH patients occurred concurrently with a severe infection, suggesting that an adrenal crisis could have contributed to these deaths.
The findings imply suboptimal glucocorticoid treatment, a point highlighted in a study of 203 CAH patients treated at specialist endocrine centres in the UK.2 Levels of the androgen precursor andostenedione were suppressed in between 10% and 29% of patients and elevated in around a third. Researcher Wiebke Arlt (University of Birmingham, UK) and colleagues found that, overall, only a third of patients had levels within the target range, and the same was true of renin levels in patients receiving mineralocorticoid replacement.
“Paediatricians have prided themselves – allegedly anyway – including myself, that we’ve done a good job,” says Hughes.
Paediatricians were not only keeping CAH patients alive, he says, but also achieving fairly good growth, helping them attain adult heights that, although lower than expected for their family, were still well within population norms.
“And then of course we hand them over to the adult physicians and they come back to us – quite rightly…”
Because the adult physicians, making detailed study of their patients’ health, were becoming aware of increased cardiometabolic morbidity in adult CAH patients. For example, Arlt et al found CAH patients were more often obese relative to the UK population, and frequently had metabolic abnormalities, with 46% having hypercholesterolaemia and 29% having insulin resistance, while around a third had osteopenia.
Similarly, Falhammar et al followed up their mortality study with a look at cardiometabolic morbidities, finding that these were almost fourfold more likely to occur in CAH patients relative to controls from the Swedish population, while cardiovascular disease was nearly threefold more common.3 Specific conditions that were elevated in CAH patients included thyrotoxicosis, venous thromboembolism, atrial fibrillation, obesity and diabetes.
Another study found evidence of cardiovascular morbidity in CAH patients at a worryingly young age.4 Ivani Silva (Universidade Federal de Minas Gerais, Belo Horizonte, Brazil) and team assessed 38 pubertal CAH patients, aged 20 years or younger, and controls matched for age, gender and pubertal status. They showed that, relative to the controls, the CAH patients had significantly increased carotid intima-media thickness – an early sign of atherosclerosis. This was not restricted to overweight patients, but was seen only in females.
So cardiometabolic morbidity is “something that’s now being taken very seriously,” says Hughes.
These studies have not only flagged high cardiometabolic risk in CAH patients, they have also begun to link it directly to CAH treatment. A cross-sectional study of 196 adults with CAH found that patients with more severe disease received higher glucocorticoid doses without achieving better disease control – higher dose was actually associated with higher androgen levels.5 Moreover, the increased glucocorticoid doses were also associated with elevated blood pressure.
Although researcher Richard Ross (Royal Hallamshire Hospital, Sheffield, UK) and team found that dexamethasone – the most potent of the glucocorticoids used in the study patients – was associated with the lowest androgen levels, this came at the expense of greater insulin resistance.
A study from Hughes’ own group took a closer look at insulin resistance in 37 CAH patients and 41 healthy controls.6 The 25 patients with classical CAH, which is diagnosed and treated early in life, had significantly greater fat mass than the controls, which the researchers attributed to the long-term effects of glucocorticoid treatment.
“Add to that the obesity epidemic and you’ve got a pretty powerful cocktail of problems,” observes Hughes.
By contrast, the 12 children with nonclassical CAH, which is usually diagnosed later in childhood, had greater lean body mass and blood pressure than the controls, and significant increases in several measures of insulin resistance. Hughes attributes these changes to the patients’ prolonged exposure to excess androgen levels in early childhood, saying that androgen “in itself is a pretty potent stimulator of insulin resistance.”
The most recent guidelines for CAH management, from 2010, acknowledge the difficulty of optimising treatment, calling it “a difficult balance between hyperandrogenism and hypercortisolism”, and noting that efforts to completely normalise androgen levels “typically result in overtreatment”.7
The guidelines also advise against long-acting glucocorticoids in children, because of their growth-suppressing effects, instead recommending hydrocortisone three times daily at the lowest possible dose to avoid compromising growth.
Hughes believes that paediatric endocrinologists “are doing much better now than we used to”, saying that the daily hydrocortisone dose, which “in the past has been too much”, has been brought down. “And that’s being translated into better growth and outcome in the short term.”
However, paediatric CAH patients experience the usual deluge of childhood colds and illnesses, each one placing the body under stress and prompting a temporary increase in hydrocortisone dose. Necessary though this is, Hughes wonders if “collectively, we have been overdosing them.”
Added to that is the highly variable pharmacokinetics of hydrocortisone, not only between different stages of childhood, but also between different children, aptly demonstrated in a paper from Peter Hindmarsh (UCL Institute of Child Health, London, UK) and Evangelia Charmandari (University of Athens Medical School, Greece).8 The researchers gave 48 children the same hydrocortisone bolus, but found that its half-life in the different patients ranged from 40 to 225 minutes. Although all children attained a similar peak plasma cortisol concentration, the speed of absorption varied widely, with time to peak concentration ranging from 20 to 118 minutes and the additional time taken for the concentration to fall below 100 nmol/L ranging from 140 to 540 minutes.
This suggests that hydrocortisone dosing should be highly individualised, and perhaps more frequent, with the study authors moving towards four doses per day on the basis of their findings.
But in some cases, clearance of hydrocortisone may be so rapid that even a six-times-daily dosing schedule is insufficient to achieve androgen control. An ingenious solution for this is continuous delivery via an adapted insulin pump, as illustrated in a case study, also by Hindmarsh.9
Pump delivery avoids gaps in hydrocortisone exposure and increased need for hydrocortisone during physiological stress can be managed simply by increasing the infusion rate or using the bolus function. Hindmarsh’s team has implemented this in three children, achieving 24-hour cortisol levels within the normal range, normalised 17-hydroxyprogesterone (17-OHP) levels and large improvements in school attendance and quality of life.
Although an effective means of mimicking physiological hormone production, an insulin pump cannot match the simplicity of oral treatment. And pharmaceutical companies are beginning to develop oral drug formulations that more closely replicate physiological production. Two slow-release formulations are currently undergoing clinical testing: Plenadren (ViroPharma SPRL, Brussels, Belgium) and Chronocort (Diurnal Ltd, Cardiff, UK).
In a phase II study of Chronocort, Ashwini Mallappa (National Institutes of Health Clinical Center, Bethesda, Maryland, USA) and colleagues found that the rates of elevated androstenedione and 17-OHP levels among 16 adult CAH patients decreased significantly with Chronocort treatment relative to conventional therapy (33.7 vs 12.0% and 33.2 vs 12.0%, respectively).10 After 6 months of Chronocort treatment, 73% and 59% had normal androstenedione and 17-OHP levels, respectively.
Hughes highlights that the more physiological replacement appeared to allow further dose reductions, with eight of the 16 patients requiring a dose reduction (although two other patients needed a dose increase).
Chronocort is taken twice daily, and therefore suppresses the overnight rise in adrenocorticotrophic hormone (ACTH) seen with Plenadren, which is taken just once daily.11
Hughes says that combating the overnight ACTH rise “probably is important, but on the other hand, if you want to be a pragmatist you’re more likely to take your medicine if it’s a once-daily thing as opposed to a twice-daily thing.”
Plenadran is a little further down the clinical testing route than Chronocort, being approved and now the subject of a post-authorisation safety registry, which includes CAH patients.12 But both formulations still need to be tested in paediatric patients.
“I hope that perhaps getting these so-called more physiological replacement regimens will in due course improve morbidity in adult life,” says Hughes.
But he adds: “It will take a generation to see that.”
The role of growth hormone (GH) has been established for many decades, but it is only with the advent of advanced molecular genetic techniques that researchers have started to piece together the precise pathways leading to growth.
Here we review seven key papers, chosen by Professor Andrew Dauber, from Cincinnati Children’s Hospital Medical Center in Ohio, USA, which document the pivotal findings that shed light on the process of signalling through the GH/insulin-like growth factor (IGF)-I axis.
The research largely represents the extreme end of the growth disorder spectrum, with a single mutation having a profound effect on a patient’s height, but Dauber stresses that “they teach us a lot about the underlying physiology and the role that those genes play in normal biology.”