title: High-Dose Hook Effect in 17-Hydroxyprogesterone Assay in a Patient with 21-Hydroxylase Deficiency.
abstract: Congenital adrenal hyperplasia (CAH) describes a group of disorders characterized by enzyme defects in adrenal steroidogenesis. 21-hydroxylase deficiency (21-OHD) is the most commonly encountered form. The analysis of steroids in pediatric cases requires high-sensitivity assays. A 14-year-old Syrian girl was referred for evaluation of short stature, amenorrhea, and hirsutism. On physical examination, breast development was Tanner stage 1. She had a phallic clitoris with a single urogenital orifice. Laboratory findings revealed primary adrenal deficiency with high androgen levels and low levels of 17-hydroxyprogesterone (17-OHP), (<0.05 ng/mL) and estrogen. This unexpected result led to suspicion of a high-dose hook effect. The measurement was repeated after 1/10 dilution of serum, and a high level of 17-OHP (115.4 ng/mL) was detected with the same test-enzyme-linked immunosorbent assay (ELISA). Simple virilizing form of CAH (21-OHD) was suspected and confirmed with genetic analysis. After initiation of glucocorticoid therapy, breast development was noted along with a decrease in testosterone level and an increase in estrogen level. To our knowledge, this is the first case report of hook effect for 17-OHP immunoassay in a patient with 21-OHD. High-dose hook effect should be suspected in patients with CAH when the test results are incompatible with one another. Additionally, this case demonstrates that a high testosterone level can block aromatase activity and consequently also estrogen production and breast development.
authors.forename: Mesut
authors.initials: M
authors.lastname: Parlak
authors.forename: Hamit Yaşar
authors.initials: HY
authors.lastname: Ellidağ
authors.affiliation: Antalya Education and Research Hospital, Clinic of Pediatric Endocrinology, Antalya, Turkey E-mail: drdoga@hotmail.com.
authors.forename: Doğa
authors.initials: D
authors.lastname: Türkkahraman
mesh_terms: D019326:17-alpha-Hydroxyprogesterone / Q000097:blood*; D000293:Adolescent; D000312:Adrenal Hyperplasia, Congenital / Q000097:blood / Q000188:drug therapy / Q000235:genetics; D005260:Female; D005938:Glucocorticoids / Q000008:administration & dosage / Q000494:pharmacology*; D006801:Humans; D007118:Immunoassay / Q000592:standards*; D012680:Sensitivity and Specificity; D013593:Syria
chemical_list: D005938:Glucocorticoids; D019326:17-alpha-Hydroxyprogesterone