Bachega T A, Billerbeck A E, Marcondes J A, Madureira G, Arnhold I J, Mendonca B B
Unidade de Endocrinologia do Desenvolvimento e Laboratório de Hormônios e Genética Molecular-LIM/42, Disciplina de Endocrinologia, Hospital das Clínicas, Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil.
Clin Endocrinol (Oxf). 2000 May;52(5):601-7. doi: 10.1046/j.1365-2265.2000.00995.x.
The diagnosis of the nonclassical form of 21-hydroxylase (NC-21OH) deficiency, established before molecular studies, is based on basal 17OH-progesterone (17OH-P) values > 15 nmol/l or ACTH-stimulated 17OH-P values > 30 nmol/l. This disease is caused by mutations in the structural gene that can be grouped into three categories: A, B and C, according to the predicted level of enzymatic activity. So, the genotype of the nonclassical form is a combination of mutations that cause moderate impairment of enzymatic activity in one allele and mutations which cause total (A), severe (B: 3%) or moderate (C: 20-60%) impairment of enzymatic activity in the other allele.
We analysed the influence of the different genotypes on 17OH-P levels in 58 patients with the nonclassical form of 21OH deficiency.
After screening for 18 mutations through Southern blotting, allele-specific polymerase chain reaction (PCR) and enzyme restriction, mutations were identified in 73% of the alleles. Patients with mutations identified in both alleles were divided into groups A/C (n = 18), B/C (n = 3) and C/C (n = 15). The basal and ACTH-stimulated 17OH-P levels in patients with A/C genotype ranged from 1.2 to 153 and 72-363 nmol/l, and in C/C genotype ranged from 0.9 to 72 and 51-363 nmol/l, respectively (P < 0.05 for stimulated levels). The lowest value of ACTH-stimulated 17OH-P levels in fully genotyped patients was 51 nmol/l. Patients with the A/C genotype presented androgen excess symptoms earlier than patients with the C/C genotype.
These data suggest an influence of genotype on phenotype and on 17OH-P levels. The high frequency of unidentified mutant alleles in nonclassical 21-hydroxylase deficiency suggests that ACTH-stimulated values of 17OH-P between 30 and 51 nmol/l have overestimated this diagnosis. Genotyping more patients with nonclassical 21-hydroxylase deficiency will help to redefine the cut-off value for ACTH-stimulated 17OH-P for correct diagnosis of this disease.
在分子研究之前确立的21-羟化酶非经典型（NC-21OH）缺乏症的诊断，是基于基础17-羟孕酮（17OH-P）值>15 nmol/L或促肾上腺皮质激素（ACTH）刺激后的17OH-P值>30 nmol/L。该疾病由结构基因突变引起，根据预测的酶活性水平可分为A、B和C三类。因此，非经典型的基因型是一个等位基因中导致酶活性中度受损的突变与另一个等位基因中导致酶活性完全（A类）、严重（B类：3%）或中度（C类：20 - 60%）受损的突变的组合。
我们分析了58例21OH缺乏非经典型患者中不同基因型对17OH-P水平的影响。
通过Southern印迹、等位基因特异性聚合酶链反应（PCR）和酶切筛选18种突变后，在73%的等位基因中鉴定出突变。两个等位基因均鉴定出突变的患者被分为A/C组（n = 18）、B/C组（n = 3）和C/C组（n = 15）。A/C基因型患者的基础和ACTH刺激后的17OH-P水平分别为1.2至153和72至363 nmol/L，C/C基因型患者分别为0.9至72和51至363 nmol/L（刺激后水平P < 0.05）。完全基因分型患者中ACTH刺激后的17OH-P水平最低值为51 nmol/L。A/C基因型患者出现雄激素过多症状的时间早于C/C基因型患者。
这些数据表明基因型对表型和17OH-P水平有影响。非经典型21-羟化酶缺乏症中未鉴定出的突变等位基因频率较高，提示ACTH刺激后的17OH-P值在30至51 nmol/L之间高估了该诊断。对更多非经典型21-羟化酶缺乏症患者进行基因分型将有助于重新确定ACTH刺激后的17OH-P的临界值，以正确诊断该疾病。
