Objective: To study the effect of adding metformin to standard steroid replacement therapy in a patient with classic salt-losing congenital adrenal hyperplasia due to 21-hydroxylase deficiency with suboptimal biochemical and clinical control.
Methods: We present the clinical and laboratory findings before and after the addition of metformin to the therapeutic regimen of the study patient.
Results: A 17-year-old girl had been diagnosed as a neonate with classic salt-losing congenital adrenal hyperplasia caused by 21-hydroxylase deficiency (CYP21A2 deficiency). She was treated with hydrocortisone, 20 mg in the morning and 10 mg at bedtime, and fludrocortisone, 50 mcg daily. While on steroid replacement, she maintained normal serum electrolytes, glucose, blood pressure, and external genitalia, but she continued to express clinical features of obesity, hirsutism, amenorrhea, and acanthosis nigricans. Elevated laboratory measurements included the following: fasting 17-hydroxyprogesterone, 3410 ng/dL; total testosterone, 326 ng/dL; and androstenedione, 390 ng/dL. She was initiated on metformin, 500 mg twice daily after meals. After 3 months, the patient lost 2 kg, amenorrhea resolved, 17-hydroxyprogesterone decreased to 1539 ng/dL, total testosterone decreased to 163 ng/dL, and androstenedione levels remained unchanged.
Conclusions: Metformin, an agent known to reduce insulin resistance, further suppressed the 17-hydroxyprogesterone concentration in a patient with classic congenital adrenal hyperplasia on steroid replacement therapy. Metformin may improve clinical and biochemical outcomes in classic congenital adrenal hyperplasia without the risk of iatrogenic Cushing syndrome.