Figure 1. Figure 1. Pedigree of a Man with Aromatase Deficiency. The proband (Subject IV-8) is indicated by the solid square. Sequence analysis of the P-450 aromatase gene was performed in the proband, his parents, two of his brothers (Subjects IV-3 and IV-5), and one of his nephews (Subject V-1). Squares denote male family members, circles female family members, slashes deceased family members, the double line consanguinity, and half-solid symbols family members heterozygous for the mutation in the P-450 aromatase gene. The values shown below the symbols are the heights (in centimeters) of the subjects in adulthood.

The proband, the second of 10 siblings, was born after an uncomplicated pregnancy. His parents were first cousins (Figure 1). The patient's early growth and pubertal development were normal, although his testicular volume remained subnormal. At 18 years of age he was 170 cm tall (25th percentile), and he continued to grow thereafter. At the age of 28 years, x-ray films of the right arm obtained after an injury revealed unfused epiphyses and osteopenia. At the age of 29 years, he married a woman who did not conceive despite regular unprotected intercourse. Semen analysis one year later7 revealed a sperm count of 1 million per milliliter (normal, >20 million) with 100 percent immotile spermatozoa. The patient was treated with 150 IU of human menopausal gonadotropin and 1000 IU of human chorionic gonadotropin intramuscularly three times weekly for four months, with no change in the sperm count.

In 1988, at the age of 31, the patient was evaluated because of a four-year history of persistent linear growth, infertility, and moderate skeletal pain, especially in the knee, that limited his ability to walk. He weighed 96.5 kg and was 187 cm tall (97th percentile). His arm span was 204 cm, and the ratio of the upper segment to the lower segment was 0.85. Physical examination revealed bilateral genu valgum. The patient's blood pressure was normal. He had normal optic fundi and no gynecomastia, acromegaly, goiter, or acanthosis nigricans. The volume of each testis was 8 ml. His penis size and pattern of pubic hair were normal. His sexual identity and psychosexual orientation as assessed by questionnaire8 were heterosexual, and his libido was normal. He had spontaneous erections sufficient for intercourse.

Table 1. Table 1. Biochemical Values before and after Six Months of Treatment with Testosterone Enanthate or Transdermal Estradiol in a Man with Aromatase Deficiency.

The patient had normal concentrations of serum testosterone, undetectable concentrations of estradiol, slightly elevated concentrations of follicle-stimulating hormone, and concentrations of luteinizing hormone at the upper limit of the normal range (Table 1). After he received an intravenous bolus dose of 100 μg of gonadotropin-releasing hormone (GnRH), his serum concentration of luteinizing hormone rose from 6 to 18 IU per liter after 60 minutes (when the peak response occurs), and the concentration of serum follicle-stimulating hormone rose from 14 to 19 IU per liter. The serum concentrations of dehydroepiandrosterone sulfate, 17-hydroxyprogesterone, androstenedione, parathyroid hormone, free thyroxine, and thyrotropin were normal. The serum concentration of growth hormone rose from 0.8 to 6.2 ng per milliliter after the administration of levodopa. The serum concentration of insulin-like growth factor I was 332 ng per milliliter (normal range at the age of 25 to 35 years, 193 to 575). The serum concentrations of total cholesterol and triglycerides were high, and the serum concentration of high-density lipoprotein (HDL) cholesterol was low (Table 1).

Figure 2. Figure 2. X-Ray Films of the Left Hand of the Proband. When the patient was first admitted, at the age of 31 and immediately before his treatment with testosterone, the bone age was 14.8 years (Panel A). Seven years later, after nine months of treatment with transdermal estradiol (50 μg twice weekly for six months, followed by 25 μg twice weekly), the bone age was greater than 16 years (Panel B). A rapid increase in bone maturation, with closure of the metacarpal and phalangeal epiphyses, is evident.

X-ray films of the left wrist and hand revealed open metacarpal and phalangeal epiphyses; the bone age was 14.8 years (Figure 2A and Figure 2B). X-ray films of the tibias, knees, and pelvis showed diffuse bone demineralization and lack of epiphyseal fusion. A bone biopsy of the iliac crest after labeling with tetracycline revealed several slightly widened areas of osteoid seams lined by active osteoblasts.

A semen analysis7 revealed a sperm count of less than 1 million per milliliter, with 100 percent immotile spermatozoa. A testicular biopsy showed hypospermatogenesis and germ-cell arrest, mainly at the level of primary spermatocytes. The karyotype was 46,XY.

In an attempt to arrest his persistent linear growth and stimulate epiphyseal closure, the patient, after giving informed consent, was treated with 250 mg of testosterone enanthate intramuscularly every 10 days for 6 months. There were no clinical, behavioral, hormonal, or metabolic changes, except for a small decrease in the serum concentration of HDL cholesterol (Table 1). His bone age did not change, and moderate bone pain persisted. He interrupted the treatment spontaneously in 1989 because of its ineffectiveness and because he believed it was rendering him irretrievably infertile.

Figure 3. Figure 3. Nucleotide Sequence of a Region of Exon 9 of the P-450 Aromatase Gene in the Patient, a Normal Subject, and the Patient's Parents. Exon 9 of the P-450 aromatase gene was amplified by PCR and sequenced directly, as described in the Methods section. A single-base change at bp 1094 (G→A) was detected. The parents were heterozygous for this mutation.

In 1995 the patient was 190 cm tall (above the 97th percentile), and his bone age and biochemical values had not changed appreciably (Table 1). The results of an oral glucose-tolerance test were normal. The similarity between his phenotype and that of a man with a mutated estrogen-receptor gene1 prompted us to analyze the patient's DNA for a mutation in that gene or in the P-450 aromatase gene. As expected from the low serum estradiol levels, the estrogen-receptor gene was normal, but there was a single G →A mutation at base pair (bp) 1094 in exon 9 of the P-450 aromatase gene, resulting in a glutamine instead of an arginine at position 365 (Figure 3). This mutation abolishes a site cleaved by the restriction enzyme Acc651; restriction analysis, used to determine the carrier status of other family members, showed that both parents were heterozygous for the mutation. Expression studies in COS-1 cells showed that the aromatase activity of the mutant protein was 0.4 percent of that of the wild-type protein in the presence of the same amount of total cellular protein, as measured by a Western blot assay corrected for the efficiency of transfection.

After giving informed consent and with the approval of the local university review board, the patient was treated with 50 μg of transdermal estradiol twice weekly. His bone pain improved after four months and resolved completely after six months. His serum concentrations of luteinizing hormone, follicle–stimulating hormone, and testosterone decreased, that of HDL cholesterol increased, and that of low-density lipoprotein (LDL) cholesterol decreased (Table 1). His fasting concentrations of serum insulin and blood glucose were normal. The serum concentrations of alkaline phosphatase and osteocalcin increased, as did the urinary excretion of pyridinoline, indicating active bone remodeling (Table 1). The bone mineral density of the lumbar spine was 0.93 g per square centimeter before treatment (normal range 9 for adolescents in Tanner stage 5, 0.96 to 1.31) and was 1.05 and 1.17 g per square centimeter after four and seven months of treatment, respectively. Epiphyseal closure was documented after nine months of therapy, with a bone age greater than 16 years (Figure 2A and Figure 2B). The treatment did not induce gynecomastia, hyperprolactinemia, or sexual dysfunction. Testicular volume and the results of semen analysis did not change. At this writing the patient is being treated with 25 μg of transdermal estradiol twice weekly.