21-Hydroxylase Deficiency medical therapy
Long-term management of CAH
Management of infants and children with CAH is complex and warrants long term care in a pediatric endocrine clinic. After the diagnosis is confirmed, and any salt-wasting crisis averted or reversed, major management issues include
- Initiating and monitoring hormone replacement
- Stress coverage, crisis prevention, parental education
- Reconstructive surgery
- Optimizing growth
- Optimizing androgen suppression and fertility in women with CAH
Glucocorticoids are provided to all children and adults with all but the mildest and latest-onset forms of CAH. The glucocorticoids provide a reliable substitute for cortisol, thereby reducing ACTH levels. Reducing ACTH also reduces the stimulus for continued hyperplasia and overproduction of androgens. In other words, glucocorticoid replacement is the primary method of reducing the excessive adrenal androgen production in both sexes. A number of glucocorticoids are available for therapeutic use. Hydrocortisone or liquid prednisolone is preferred in infancy and childhood, and prednisone or dexamethasone are often more convenient for adults.
The glucocorticoid dose is typically started at the low end of physiologic replacement (6-12 mg/m2 but is adjusted throughout childhood to prevent both growth suppression from too much glucocorticoid and androgen escape from too little. Serum levels of 17OHP, testosterone, androstenedione, and other adrenal steroids are followed for additional information, but may not be entirely normalized even with optimal treatment. (See Glucocorticoid for more on this topic.)
Mineralocorticoids are replaced in all infants with salt-wasting and in most patients with elevated renin levels. Fludrocortisone is the only pharmaceutically available mineralocorticoid and is usually used in doses of 0.05 to 2 mg daily. Electrolytes, renin, and blood pressure levels are followed to optimize the dose.
Optimizing growth in CAH
One of the challenging aspects of long-term management is optimizing growth so that a child with CAH achieves his or her height potential because both undertreatment and overtreatment can reduce growth or the remaining time for growth. While glucocorticoids are essential for health, dosing is always a matter of approximation. In even mildly excessive amounts, glucocorticoids slow growth. On the other hand, adrenal androgens are readily converted to estradiol, which accelerates bone maturation and can lead to early epiphyseal closure. This narrow target of optimal dose is made more difficult to obtain by the imperfect replication of normal diurnal plasma cortisol levels produced by 2 or 3 oral doses of hydrocortisone. As a consequence, average height losses of about 4 inches (10 cm) have been reported with traditional management.
Traditionally, pediatric endocrinologists have tried to optimize growth by measuring a child every few months to assess current rate of growth, by checking the bone age every year or two, by periodically measuring 17OHP and testosterone levels as indicators of adrenal suppression, and by using hydrocortisone for glucocorticoid replacement rather than longer-acting prednisone or dexamethasone.
The growth problem is even worse in the simple virilizing forms of CAH which are detected when premature pubic hair appears in childhood, because the bone age is often several years advanced at the age of diagnosis. While a boy (or girl) with simple virilizing CAH is taller than peers at that point, he will have far fewer years remaining to grow, and may go from being a very tall 7-year-old to a 62-inch 13-year-old who has completed growth. Even with adrenal suppression, many of these children will have already had central precocious puberty triggered by the prolonged exposure of the hypothalamus to the adrenal androgens and estrogens. If this has begun, it may be advantageous to suppress puberty with a gonadotropin-releasing hormone agonist such as leuprolide to slow continuing bone maturation.
In recent years some newer approaches to optimizing growth have been researched and are beginning to be used. It is possible to reduce the effects of androgens on the body by blocking the receptors with an antiandrogen such as flutamide and by reducing the conversion of testosterone to estradiol. This conversion is mediated by aromatase and can be inhibited by aromatase blockers such as testolactone. Blocking the effects and conversions of estrogens will allow use of lower doses of glucocorticoids with less risk of acceleration of bone maturation. Other proposed interventions have included bilateral adrenalectomy to remove the androgen sources, or growth hormone treatment to enhance growth.
For a more extensive review of the difficulties of optimizing growth, see Migeon CJ, Wisneiewski AB. Congenital adrenal hyperplasia owing to 21-hydroxylase deficiency: growth, development, and therapeutic considerations. Endocrinol Metab Clin N Am 30:193-206, 2001.