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LAB TESTS FOR CAH:IMPORTANT THINGS TO
KNOW
2016 CONGENITAL ADRENAL HYPERPLASIA
PATIENT & FAMILY SUMMIT
NOVEMBER 12, 2016
JACK FUQUA, M.D.
PROFESSOR OF CLINICAL PEDIATRICS
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WHY DO TESTS FOR CAH?
• Diagnosis
• Newborn screening
• Evaluation of suspected newborns
• Precocious puberty
• Abnormal reproductive function and signs of virilization in teens/women
• Monitoring of treatment
• Ensure proper doses
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CONTROL OF STEROID SECRETION
• HPA axis
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NORMAL STEROIDSYNTHESIS
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NORMAL STEROID SYNTHESIS
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STEROID SYNTHESIS IN CAH
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STEROID SYNTHESIS IN CAH
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HOW ARE THESE SUBSTANCES MEASURED?
Steroid
• Immunoassays
• Routinely available at most labs
• Can get results quickly
• May be difficult to distinguish between similar substances
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HOW ARE THESE SUBSTANCES MEASURED?
• Tandem mass spectrometry
• Able to distinguish between similar substances
• Not routinely available at hospital or community labs
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ISSUES IN CAH MONITORING
• Time of blood tests
• Time of last medication
• Recent stress dosing
• Stress of blood drawing
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CONTROL OF STEROID SECRETION
• Increased activity of HPA axis in early morning
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STEROID SECRETORY PATTERN IN CAH
• 36 children with CAH
• Every 20 minute measurement of cortisol and 17OHP
• Usual hydrocortisone doses
Charmandari, et al. JCEM 86:4679, 2001
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TIME OF DAY EFFECTS
• Like cortisol, 17OHP is low overnight
• Both increase at about 4:00 AM
• Regardless of degree of control
• Better control means lower overall levels
• Easier to suppress later in the day
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PROXIMITY TO STEROIDDOSING
• Rapid decline in 17OHP and androstenedione after hydrocortisone
• With the morning dose, the lowest levels are 3-4 hours afterwards
• Testosterone is more steady
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OTHER CONSIDERATIONS IN TESTING
• Effects of stress dosing
• Suppression of 17OHP, androstenedione, and testosterone
• May last for days after administration
• Avoid lab tests soon after stress dosing
• Stress of blood drawing
• Physical or emotional stress (pain, anxiety) leads to rapid increases in 17OHP
• Androstenedione and testosterone are less responsive
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PLASMA RENIN ACTIVITY
• Assesses mineralocorticoid effect
• High in untreated salt-wasting CAH
• Used to decide on fludrocortisone (Florinef) dose and salt intake
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ALTERNATIVE TESTING APPROACHES
• Salivary testing
• 24 hour urine collection
• Filter paper blood spot
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BONE AGE
• Done to measure skeletal maturity
• Greulich and Pyle atlas, ©1950
• Compares child’s x-ray of hand/wrist to a series of x-rays from children of different ages
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BONE AGE• Advanced bone ages
predict earlier attainment of adult height
• Example: An 8 year old girl with a bone age of 11 only has 3 years of growth remaining instead of 6 years
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OTHER CONSIDERATIONS IN MONITORING CAH
• Growth chart
• Bone age
• Clinical factors