Anthropometry in Congenital Adrenal Hyperplasia

Abstract

Congenital adrenal hyperplasia (CAH) is a monogenic disorder of the adrenal cortex with cortisol deficiency and androgen excess affecting anthropometric parameters throughout the entire life. Glucocorticoids are the mainstay of therapy and anthropometry is vital in judgment and adjustment of the treatment. Treatment involves a difficult balance, in which both over- and undersubstitution will result in an increased risk of short final height. Hence, the majority of patients with CAH have attained a final height below their potential. However, improvements in management have resulted in more patients reaching their target height. Earlier, obesity was common in CAH. Nowadays the situation may have improved, weight in these patients does not differ from that in the general population. However, the shorter stature of CAH patients results in an elevated body mass index (BMI) in most reports on both children and adults, and patients aged >30 years may have a higher waist to hip ratio. BMI may give an unreliable estimate of body fat in CAH since, females in particular may experience high androgen levels leading to increased muscle mass. Moreover, owing to the exposure to raised androgens during fetal life, many girls and women with CAH show more gender-atypical behavior regarding choice of profession and leisure time interests with increased physical activity as a consequence. These individuals may then show an elevated BMI as a result of increased muscle (lean) mass, but without increased fat mass. On the other hand, in overtreatment with glucocorticoids, lean mass may be low and BMI may underestimate fat mass. Dual energy X-ray absorptiometry (DXA) provides a more accurate and reliable way of measuring fat and lean mass in males and females affected by CAH. DXA has demonstrated increased fat mass in CAH, but sometimes also, especially in women, increased lean mass. Other anthropometric characteristics of females with CAH are a lower ratio of the length of the index finger to the ring finger compared to female controls of the same ethnicity, indicating a more masculine-typical ratio. The virilization of external genitals seen predominantly in classic CAH includes a longer clitoris than normal unless operated upon. Benign testicular adrenal rest tumors are common and in about one third of patients may reach a size large enough to become palpable. In conclusion, anthropometry is a central part of the management of CAH; however, due to the special features of CAH, the interpretations of anthropometry may differ.