Cardiovascular risk profile in pediatric CAH patients: a cross-sectional study

Congenital adrenal hyperplasia (CAH) is a disorder of adrenal steroidogenesis.
In 95% of cases it is caused by 21-hydroxylase deficiency.1 Deficiency of
21-hydroxylase results in impaired adrenal synthesis of cortisol and often also
of aldosterone leading to increased secretion of ACTH, adrenal hyperplasia and
excessive production of adrenal precursors before the enzymatic bloc such as 17
hydroxyprogesterone. The production of adrenal androgens is not disturbed.
Therefore, adrenal hyperplasia will lead to excessive production of adrenal
androgens. Treatment with glucocorticoids and, if necessary, mineralocorticoids
prevents adrenal crises and suppresses abnormal secretion of adrenal androgens.
Usually supraphysiological doses of glucocorticoids are needed to suppress
androgen levels. In the case of illness the glucocorticoid dosage even has to
be increased.
Patients with CAH, who are treated with supraphysiological doses of
glucocorticoids, are at risk of developing signs and symptoms of Cushing*s
syndrome. As hypercortisolism is associated with hypertension, obesity with
abdominal fat accumulation and diabetes mellitus, it is not unlikely that
patients with CAH may show an adverse cardiovascular and metabolic risk
profile, possibly leading to a reduced life expectancy. Furthermore,
mineralocorticoid excess may play a role in the development of high blood
pressure. Only recently, we systematically reviewed all the available data on
body mass index (BMI), body composition, blood pressure, insulin sensitivity
and lipid profiles in adult and pediatric CAH patients. Indeed, the literature
suggests that adult CAH patients seem to have a high risk to cluster a number
of risk factors, resembling the criteria of the metabolic syndrome. Several
studies have been performed evaluating cardiovascular risk factors in both
adult and pediatric CAH patients. Some of these studies were performed within
our study group. These studies show that adult CAH patients are characterized
by an elevated BMI, a changed body composition (towards an increased fat mass
and more abdominal fat), insulin resistance, and elevated blood pressure
levels.5 Furthermore, an increased intima-media thickness (IMT) was described
in adult CAH patients. An increased IMT has been described as a surrogate
marker of atherosclerosis and consequently a higher cardiovascular risk. Data
on cardiovascular risk factors in pediatric CAH patients is scarce. During
childhood, a tendency towards high blood pressure and elevated BMI have been
shown. One study showed pediatric CAH patients (both caused by 21-hydroxylase
deficiency and other deficiencies) to be insulin resistant. Unfavorable changes
in the cardiovascular risk profile may be due to both effects of treatment
(glucocorticoids, mineralocorticoids) and high androgen levels. No systematic
research on cardiovascular risk factors has been performed in pediatric CAH
patients. Because several of the risk factors were found abnormal in adult
patients, evaluation in childhood is essential.

We hypothesize that cardiovascular risk factors may already be present during
childhood in CAH patients. Therefore, we will perform a cross-sectional study
in CAH patients aged 1-16 years evaluating blood pressure, lipid profile,
insulin sensitivity, cardiac function (electrocardiography (ECG),
echocardiography), IMT, body composition (Dual Energy Xray Absorptiometry
(DEXA) scan), and several biochemical cardiovascular risk markers. Furthermore,
we want to incorporate recently developed and well-established echocardiography
techniques (Tissue Doppler, strain en strain rate imaging) to identify early
signs of myocardial dysfunction.

Patients and methods and data collection
Patients
All CAH patients, due to 21-hydroxylase deficiency, with biochemical and
genetically proven CAH, aged 0-16 years treated within the Radboud University
Nijmegen Medical Centre (n=80) will be included in this study. Baseline
characteristics (date of birth, mutation analysis, target height (SDS), current
height (SDS), hydrocortisone and fludrocortisones dose, bone age) will be
collected for all patients from their individual electronic patients medical
file.
Exclusion criteria will be:
• Inability to give written consent for the study.
• Known co-morbidity: cardiac disease, renal disease, co-medication that
interferes with blood pressure.
Methods
Written informed consent will be asked to both parents and children above 12
years old.
Each participant will visit the hospital on two consecutive days that will be
combined with a regular visit to the outpatient clinic. On the first day,
participants will visit the hospital at 8.30 a.m. after an overnight fast.
Before taking morning medication a maximum of 38 ml blood (in neonates a
minimum of 2.5 ml and a maximum of 21 ml) will be taken to assess the following
biochemical markers: fasting glucose, HbA1C, insulin, lipid profiles (total
cholesterol, HDL cholesterol, LDL cholesterol, triglycerides), plasma
catecholamines and metanephrines, aldosterone, renin, ACTH, leptin,
adiponectin , hsCRP, IL-6, IL-18, TPA, PAI-1. Insulin resistance (IR) will be
estimated using the homeostasis model assessment (HOMA) method [IR = insulin
(µmol/ml) x glucose (mmol/l)/22.5]. Residual blood will be stored anonymised
for future research.
Afterwards all participants will have a routine visit scheduled to their
treating pediatric endocrinologist in our outpatient clinic. The participants
receive a physical examination including anthropometric measurements and hip
and waist circumference. Subsequently, blood pressure will be assessed under
real-life conditions using 24 hours ambulatory blood pressure monitoring
(24h-ABPM) in patients older than 5 years. During 24 hours blood pressure
measurements patients and their parents will register physical activities and
time of going to sleep and waking up in a diary. Furthermore, the patients will
receive a container to collect all urine during 24 hours. A urinary steroid
profile will be analyzed to be informed about hormonal control in the treated
CAH patients and to measure other steroids and adrenal metabolites that might
be elevated in CAH patients. On the second day, participants will return to the
hospital for disconnection of the ambulatory blood pressure monitoring device
and to return the collected urine. Echocardiography, including recently
developed techniques (Tissue Doppler, strain en strain rate imaging) will be
performed according to a strict protocol by an experienced echo technician and
supervised by one experienced pediatric cardiologist (LK) to evaluate cardiac
function with left ventricular hypertrophy as main outcome measure. IMT
measurement will be performed attached to the echocardiography protocol in
order to determine the level of atherosclerosis. Additionally an ECG will be
performed. A DEXA scan will be performed to evaluate body composition in
patients older than 12 years. A DEXA total-body scanner will be used to obtain
regional and whole body composition measurements using a three-compartment
model of body composition: lean tissue mass (LTM), fat tissue mass (FTM), and
bone mineral content (BMC). LTM, FTM and BMC will be determined using software
algorithms based on derived regression equations. Percentage of body fat by
DEXA for total body will be calculated using the formula:100•FTM/ (FTM + LTM +
BMC). Scanning time will be approximately 20 to 30 minutes.
Collected data will be compared to internationally accepted reference values
for the different cardiovascular risk markers therefore a control group is not
necessary.

Hospital visits on 2 consecutive days for several non-invase diagnostic tests.
24-h bloodpressure measurement.
DEXA total body scan.
Blood test.