Impact of estrogen replacement therapy in a male with congenital aromatase deficiency caused by a novel mutation in the CYP19 gene

Recent reports of the impact of estrogen receptor a and aromatase deficiency have shed new light on the importance of estrogen for bone formation in man. We describe a novel mutation of the CYP19 gene in a 27-yr-old homozygous male of consanguinous parents. A C to A substitution in intron V, at position -3 of the splicing acceptor site before exon VI of the CYP19 gene, is the likely cause of loss of aromatase activity. The mRNA of the patient leads to a frameshift and a premature stop codon 8 nucleotides downstream the end of exon V. Both parents were shown to be heterozygous for the same mutation. Apart from genua valga, kyphoscoliosis, and pectus carniatus, the physical examination was normal including secondary male characteristics with normal testicular size. To substitute for the deficiency, the patient was treated with 50 jig transdermal estradiol twice weekly for 3 months, followed by 25 mug twice weekly. After 6 months estrogen levels (<20 at baseline and 45 pg/ml at 6 months; normal range, 10-50) and estrone levels (17 and 34 ng/ml; normal range, 30-85) had normalized. Bone maturation progressed and the initially unfused carpal and phalangeal epiphyses began to close within 3 months and were almost completely closed after 6 months. The bone age, assessed by roentgenographic standards for bone development by Gruelich and Pyle, was 16.5 at baseline and 18-18.5 yr after 6 months of treatment. Bone density of the distal radius (left), assessed by quantitative computed tomography, increased from 52 to 83 mg/cm(3) (normal range, 120-160) and bone mineral density of the lumbar spine, assessed by dual-energy x-ray-absorptiometry, increased from 0.971 to 1.043 g/cm(3) (normal range, > 1.150). Osteocalcin as a bone formation parameter increased from 13 to 52 mug/l (normal range, 24-70) and aminoterminal collagen type I telopeptide as a bone resorption parameter increased from 62.9 to 92.4 nmol/ mmol creatinine (normal range, 5-54). Semen analysis revealed oligoazoospermia (17.4 million/ml; normal >20) at baseline. After 3 months of treatment, the sperm count increased (23.1 million/ml) and decreased rapidly (1.1 million/ml) during the following 3 months. The sperm motility was reduced at baseline and decreased further during treatment. Area under the curve of insulin, C-peptide, and blood glucose levels during oral glucose tolerance test decreased after 6 months (insulin: 277 vs. 139 muU/ml.h; C-peptide 52 vs. 15 ng/m.h; area under the curve glucose: 17316 vs. 12780 mg/d-min). Triglycerides (268 vs. 261 mmol/liter) and total cholesterol levels (176 vs. 198 mmol/liter) did not change significantly, but the low-density lipoprotein/high-density lipoprotein ratio decreased from 5.37 to 3.56 and lipoprotein (a) increased from 19.9 to 60.0 mg/dl (normal range, <30). In this rare incidence of estrogen deficiency, estrogen replacement demonstrated its importance for bone mineralization and maturation and glucose metabolism in a male carrying a novel mutation in the CYP19 gene.