The interference of DEHP in precocious puberty of females mediated by the hypothalamic IGF-1/PI3K/Akt/mTOR signaling pathway.

DEHP is reported to cause precocious puberty of females in both humans and rodents, but the underlying mechanisms were largely unknown. This study was designed to clarify the effects and the mechanisms of DEHP on the pathogenesis of sexual precocity. Prepubertal female rats were treated with DEHP for 4 weeks. Key organs were analyzed in control conditions and after exposure to 0.2, 1, and 5 mg/kg/day DEHP in pubertal female rats. To determine the role of the IGF-1/PI3K/Akt/mTOR signaling pathway in DEHP-induced female precocious puberty, 36 rats were treated with 5 mg/kg/day DEHP to establish a model of female precocious puberty. And we investigated the expression of genes and proteins related to IGF-1 pathway in rat hypothalamus after treatment with inhibitors. In the present study, we observed that DEHP treatment resulted in earlier vaginal opening time, higher number of Nissl bodies in the hypothalamus neurons, lower apoptosis of hypothalamic cells, higher IGF-1 and GnRH levels in the serum and hypothalamus. DEHP could also upregulated the expression of IGF-1/PI3K/Akt/mTOR pathway and GnRH in the hypothalamus of adolescent female rats, and inhibition of IGF-1R and mTOR in hypothalamus could block the activation of Kiss-1, GPR54, and GnRH by DEHP. In summary, our study suggested that DEHP might activate the hypothalamic GnRH neurons prematurely through the IGF-1 signaling pathway and promote GnRH release, leading to the initiation of female sexual development. Our results provide a new molecular mechanism underlying reproductive and developmental toxicity in pubertal female rats induced by DEHP.

Association of aromatase (TTTA)n repeat polymorphisms with central precocious puberty in girls.

OBJECTIVE: Precocious puberty is characterized by early activation of the pituitary-gonadal axis. Oestrogen is the final key factor to start the onset of puberty. The cytochrome P450 19A1 (CYP19A1) gene encodes an aromatase that is responsible for the conversion of androgens to oestrogen, which is a key step in oestrogen biosynthesis. The aim of this study was to identify CYP19A1 gene mutations or polymorphisms in girls with central precocious puberty (CPP). METHODS: We evaluated the frequency of allelic variants of the CYP19A1 exons and the tetranucleotide tandem repeat (TTTA)n in intron 4 in 203 idiopathic central precocious puberty (CPP) girls and 101 normal healthy women. RESULTS: The genotype analysis of the CYP19A1 (TTTA)n polymorphism revealed six different alleles ranging from seven to 13 repeats. Among the six different repeat alleles detected in this study, the (TTTA)13 repeat allele was only detected in the patient group and carriers of the (TTTA)13 allele were significantly associated with an increased risk of CPP (OR = 1·509, 95% CI = 1·425-1·598, P = 0·033). Carriers of the (TTTA)13 repeat allele were significantly younger at pubertal onset and had higher levels of oestrogen than noncarriers of the (TTTA)13 repeat allele. Although nine polymorphisms were detected in exons of the CYP19A1 gene, no clinical significance was observed. CONCLUSION: In this study, carriers of a higher repeat (TTTA)13 polymorphism in intron 4 of the CYP19A1 gene had higher levels of oestrogen. Those carrying the (TTTA)13 repeat allele may have a higher risk of developing CPP.

Refractory hypertension and isosexual pseudoprecocious puberty associated with renin-secreting ovarian steroid cell tumor in a girl.

Steroid cell tumor, not otherwise specified (NOS), are rare ovarian tumor, in addition, it is more rare in children. The majority of these tumors produce several steroid hormones, particularly testosterone. Estrogen also secreted by steroid cell tumor, NOS, but it is uncommon. Furthermore, hypertension is an infrequent sign in steroid cell tumor, NOS. An 8.5-yr-old girl with hypertension and frequent vaginal spotting visited at our clinic. On laboratory evaluation, secondary hypertension due to an elevated plasma renin level and isosexual pseudoprecocious puberty was diagnosed. Right solid ovarian mass was detected in radiologic tests. She underwent a right ooporectomy and it revealed renin and progesterone receptor positive steroid cell tumor, NOS. After operation, her blood pressure returned to normal level and vaginal bleeding disappeared. Even though this case is very rare, when hypertension coincides with virilization or feminization, a renin-secreting ovarian steroid cell tumor, NOS, should be considered.

Use of aromatase inhibitors in children and adolescents: what's new?

PURPOSE OF REVIEW: Aromatase inhibitors have been reported to increase height prediction in boys with short stature, and in boys and girls with gonadotropin-independent precocious puberty. The following review discusses data published since 2008 regarding the safety and efficacy of aromatase inhibitors in pediatric patients. RECENT FINDINGS: Third-generation aromatase inhibitors in combination with antiandrogens appear effective in preventing bone age advancement and virilization in boys with familial male-limited precocious puberty (FMPP). Letrozole, but not anastrozole, decreased bleeding episodes and bone age advancement in girls with McCune-Albright syndrome (MAS), despite ovarian enlargement. Letrozole-treated boys with idiopathic short stature (ISS) had no loss of bone density but were noted to have more vertebral abnormalities than a placebo group. Two years of letrozole therapy did not increase predicted adult height in pre and peripubertal boys with ISS when re-assessed 4 years after the treatment period. SUMMARY: Aromatase inhibitors together with an antiandrogen appear to be a very promising treatment for FMPP. Further longer-term studies with letrozole are needed in MAS. The prevalence of vertebral deformities should be evaluated prospectively in patients treated with aromatase inhibitors. Adult height data are still lacking in pediatric patients treated with aromatase inhibitors. Two years of therapy in pre and peripubertal short boys does not appear to increase adult height. Hemogram, lipids, and bone density should be periodically assessed in treated patients. Further controlled studies are needed to demonstrate safety and efficacy of aromatase inhibitors in pediatric patients.

Lack of association between common polymorphisms in the 17beta-hydroxysteroid dehydrogenase type V gene (HSD17B5) and precocious pubarche.

BACKGROUND: 17beta-Hydroxysteroid dehydrogenase (type V; HSD17B5) is a key enzyme involved in testosterone production in females. A single nucleotide polymorphism (SNP) in the promoter region of its gene was recently found to be associated with polycystic ovary syndrome (PCOS) and its related hyperandrogenaemia. Precocious pubarche (PP) is a clinical entity pointing to adrenal androgen excess from mid-childhood onward and is associated with ovarian androgen excess from puberty onward. It is therefore a strong risk factor for PCOS. METHODS: To investigate associations between this promoter SNP along with three exonic SNPs (one non-synonymous and two synonymous) from the same gene, and PP, a case-control study was performed in 190 girls with PP (84 of which were also tested for functional ovarian hyperandrogenism) from Barcelona, Spain and 71 healthy controls. Clinical features and hormone concentrations relevant to hyperandrogenism were compared by HSD17B5 genotype and haplotype. RESULTS: Neither HSD17B5 genotypes nor haplotype were associated with PP, or subsequent androgen excess in girls from Barcelona (all P>0.05). CONCLUSIONS: HSD17B5 SNPs predicted to have functional effects do not appear to be a risk factor for PP in girls from Barcelona, despite these girls being at high risk of developing androgen excess in adulthood.

Associations between common variation in the aromatase gene promoter region and testosterone concentrations in two young female populations.

We recently reported association between a coding-region single nucleotide polymorphism (SNP50) in the aromatase gene that encodes a key enzyme in testosterone metabolism, with risk for the development of precocious pubarche and circulating testosterone concentrations in two independent female populations. We have now explored further association with variation in the promoter-region of the aromatase gene. We genotyped six promoter-region haplotype-tag SNPs in young women from Oxford, UK (n = 109), and in girls with precocious pubarche (n = 186) and controls (n = 71) from Barcelona, Spain. Aromatase distal promoter-region variation was associated with plasma testosterone concentrations in both Oxford (r(2) = 18.3%, p = 0.01) and Barcelona (r(2) = 8.5%, p = 0.03) females. These associations were independent of SNP50, but appeared to be dependent on different SNPs in Oxford (r(2) = 13.7%, p = 0.006 with SNPs 11 (p = 0.009), 28 (p = 0.02) and 39 (p = 0.06)) and Barcelona (r(2) = 5.9%, p = 0.002 with SNP43 (p = 0.002)) populations. Aromatase distal promoter-region variation was also associated with PCOS symptom score in Oxford women (r(2) = 14.5%, p = 0.048), but, unlike SNP50, was not associated with precocious pubarche risk in Barcelona girls. In conclusion, aromatase distal promoter-region variation appears to have functional consequences for plasma testosterone concentrations in females. The variable associations with androgen-related clinical features could possibly reflect the tissue-specific promoters of the aromatase gene.

Congenital adrenal hyperplasia in the Bahamas due to 21-hydroxylase deficiency.

OBJECTIVE: To determine the frequency of 21-hydroxylase deficiency in The Bahamas and the spectrum of this disorder METHODS: Patients referred for evaluation of virilization, precocious puberty, ambiguous genitalia and salt wasting had blood taken for 17-hydroxyprogesterone (17-OH progesterone) which was measured by Enzyme-Linked Immunosorbent Assay (ELISA). RESULTS: Nine patients had elevated 17-OH progesterone levels--confirming 21-hydroxylase deficiency. Range of levels was 174.9 nmol/l to 81678.7 nmol/L (normal less than 13 nmol/L). There were six females and three males and the age at diagnosis ranged from 21 days to 16 years. Five had precocious development, three had salt wasting, and there was one with virilization. One of the salt wasters had ambiguous genitalia. Incidence of 2l-hydroxylase deficiency--20/100,000; salt wasting--35/100,000; the prevalence of 21-Hydroxylase deficiency 10/100,000). CONCLUSION: The frequency of 21-Hydroxylase deficiency in The Bahamas is one of the highest worldwide.

[Congenital adrenal hyperplasia due to 11-beta-hydroxylase deficiency]. / Hiperplasia supra-renal congênita por deficiência de 11-beta-hidroxilase.

The objective of this article is to relate the diagnostic and clinical evolution of a 15 year old patient with a congenital adrenal steroidogenesis dysfunction that can present as hypertension diagnosed later in life (adolescence), virilization or salt wasting (birth and childhood).

High incidence of molecular defects of the CYP21 gene in patients with premature adrenarche.

On the basis of hormonal studies, the incidence of defective steroidogenesis in children with premature adrenarche (PA) in the various reports ranges from 0-54%. Molecular studies have not been reported to date. The aim of the present study was to search for defects in the CYP21 gene in children with PA and to detect possible correlations of the molecular defect to pertinent hormonal and clinical data. In 48 children with PA (40 females and 8 males) and without signs of virilization, a Synachten test and molecular studies were carried out. DNA analysis was performed using the Southern blot technique and allele-specific PCR. Synachten (0.25 mg) was given i.v., and 17-hydroxyprogesterone and cortisol were determined at 0 and 60 min. At baseline, delta4-androstenedione, dehydroepiandrosterone sulfate, and 11-deoxycortisol were also determined. Bone age was evaluated using the Greulich and Pyle atlas. Abnormal genotype was detected in 45.8% of the studied subjects; 8.3% were homozygotes, with genotypes concordant with the nonclassical phenotype of 21 hydroxylase deficiency, and 37.5% were heterozygotes for 9 different molecular defects of the CYP21 gene. The children with no detectable molecular defect were designated normal. The 60 min post-Synachten values in homozygotes (17.9 +/- 7.1 ng/mL) and heterozygotes (7.1 +/- 3.6 ng/mL) were significantly higher than that in normal subjects (3.3 +/- 1.5 ng/mL), but with significant overlapping of values. The mean difference between bone age and chronological age differed in the three groups with overlapping values. The basal delta4-androstenedione level was lower in the normal subjects (0.65 +/- 0.3 ng/mL) than in those with abnormal genotype (1.1 +/- 0.8 ng/mL). The data indicate that the incidence of molecular defects in PA is quite high. The CYP21 heterozygocity is clinically expressed in some subjects prepubertally. In a significant number of cases the genotype cannot be predicted by the age of onset of PA, the mean difference between bone age and chronological age, or the results of a Synachten test. Follow-up of these children through puberty is imperative and may reveal the clinical significance of the molecular defect, namely more hypertrichosis, intense acne, early puberty, possible abnormal menses, and/or fertility problems in the affected.

Genetic defects of steroidogenesis in premature pubarche.

Twenty three patients (19 girls, 4 boys) presented with typical features of premature pubarche between the ages of 2-7 yr. The patients were studied for the presence of an adrenal steroidogenic defect by ACTH stimulation testing (Cortrosyn, 0.25 mg iv bolus dose). Based on published nomogram standards for serum 17-hydroxyprogesterone (17-OHP), seven patients (30%) were diagnosed as having the nonclassical symptomatic form of 21-hydroxylase deficiency [mean post ACTH 4244 +/- 1113 (SD) ng/dl]. Three patients (13%) were diagnosed to have a mild form of 3 beta-hydroxysteroid dehydrogenase deficiency based upon the response of serum delta 5-17-hydroxypregnenolone (delta 5-17P) and dehydroepiandrosterone, and the ratio of delta 5-17P/17-OHP to ACTH stimulation (delta 5-17P: 1543 +/- 272 ng/dl vs. Tanner stage I control subjects, 350 +/- 197 ng/dl; dehydroepiandrosterone: 675 +/- 190 ng/dl vs. Tanner stage I control subjects, 82 +/- 79 ng/dl; delta 5-17P/17-OHP: 8.1 +/- 2.6 vs. Tanner stage I control subjects, 1.4 +/- 0.6). No enzyme defect could be identified in the remaining 13 patients (57%). Eleven patients with premature pubarche, with and without an adrenal enzymatic defect, underwent dexamethasone suppression. In all patients the measured steroid levels were suppressed. Thus, the dexamethasone suppression test alone did not distinguish the pathogenesis of premature pubarche. In conclusion, premature pubarche is more commonly due to a partial enzyme defect in adrenal steroidogenesis than has been previously recognized.

Studies of 3 beta-hydroxysteroid dehydrogenase genes in infants and children manifesting premature pubarche and increased adrenocorticotropin-stimulated delta 5-steroid levels.

Classic 3 beta-hydroxysteroid dehydrogenase (3 beta HSD) deficiency congenital adrenal hyperplasia (CAH) results from a mutation in the type II 3 beta HSD gene encoding adrenal and gonadal 3 beta HSD. We investigated the type II and type I 3 beta HSD gene sequences in 15 infants and children with premature pubarche (PP; mean/range of age at PP, 4/0.08-9 yr) and elevated ACTH-stimulated delta 5 precursor steroid levels. Compared to Tanner I control subjects of similar age, ACTH-stimulated hormonal levels were at 2.3-10.7 SD for 17-hydroxypregnenolone (delta 5-17P) in all PP subjects, at 2.2-17 SD for dehydroepi-androsterone (DHEA) and 2.4-5.6 SD for the delta 5-17P/cortisol (F) ratio in all PP subjects except 1 infant, and at 2.3-10 SD for the DHEA/ androstenedione (delta 5-A) ratio in 8 PP subjects. Compared to Tanner II normal children, the hormonal levels were at 3-8 SD for delta 5-17P in all 13 PP children, at 2.3-4.7 SD for the delta 5-17P/F ratio in 6 PP children, and at 2.3-6.5 SD for DHEA and 3.5-9 SD for the DHEA/delta 4-A ratio in 7 PP children. Type II 3 beta HSD gene sequences, including regions of a putative promoter, all exons (I, II, III, and IV), and exon-intron boundaries, were normal in all subjects. Sequences of the type I 3 beta HSD gene encoding extraadrenal and extragonadal 3 beta HSD were normal in the 6 patients tested. The ACTH-stimulated delta 5-17P levels and delta 5-17P/F ratios in the PP children without type II 3 beta HSD gene mutation were exceedingly lower than the respective reported hormonal data for children with 3 beta HSD deficiency CAH with proven type II 3 beta HSD gene mutation. The ACTH-stimulated DHEA levels and DHEA/delta 4-A ratios were not exceedingly different between the children with and without type II 3 beta HSD gene mutation. These findings suggest that the degree of ACTH-stimulated delta 5 precursor steroid abnormality, such as delta 5-17P levels up to 10 SD above the normal mean level found in our PP patients, is not caused by a mild variant of 3 beta HSD deficiency CAH resulting from type II or type I 3 beta HSD gene mutation. The hormonal criterion for ACTH-stimulated delta 5-17P levels in patients with mild variant 3 beta HSD deficiency, therefore, is predicted to be higher than 10 SD above the normal mean value.

Familial hyperestrogenism in both sexes: clinical, hormonal, and molecular studies of two siblings.

Familial hyperestrogenism is a rare clinical condition of unknown etiology in which patients present excessive androgen to estrogen conversion. Excessive aromatization is primarily ascribed to abnormalities in the CYP19. Mice that lack steroid 5alpha-reductase type 1 also exhibit hyperestrogenism due to an increased availability of androgen precursors. Here we studied two adult siblings, born to unrelated parents, who presented clinical and hormonal evidence of estrogen excess. The man was treated with topical dihydrotestosterone, which promoted adequate virilization. The woman was treated with anastrazole, a potent aromatase inhibitor, with normalization of menstrual cycles. Genetic linkage to the steroid 5alpha-reductase type 1 gene (SRD5A1) was ruled out in this family. A similar analysis did not rule out linkage to CYP19, although no mutation was identified in the coding region of this gene. Aromatase mRNA was at least 10-fold more abundant in the female patient's skin fibroblasts vs. the control. Southern analysis of genomic DNA did not reveal rearrangements or amplification of the coding region of CYP19. We conclude that the phenotype of familial hyperestrogenism includes prepubertal gynecomastia, hypogonadism, and short stature in men, and precocious thelarche, macromastia, enlarged uterus, and menstrual irregularities in women. Topical dihydrotestosterone is an efficient alternative treatment in men with hyperestrogenism; in addition, second generation aromatase inhibitors are useful in both sexes.

Adrenal steroidogenic function in a black and Hispanic population with precocious pubarche.

Adrenal steroidogenic function was evaluated in 34 children with precocious pubarche (PP; onset of pubic hair, less than 8 yr in girls and less than 9 yr in boys). The adrenal steroid response to an iv bolus of ACTH-(1-24) in the patients (aged 9 months to 9 7/12 yr) was compared to that in 16 normal controls (prepubertal, n = 9; Tanner stage II pubic hair, n = 7). The patient population consisted of 20 Hispanics (17 from the Dominican Republic), 13 black Americans, and 1 black Haitian. All patients had normal stimulated levels of 17-hydroxyprogesterone (17-OHP), 11-deoxycortisol (compound S), and desoxycorticosterone, thereby ruling out 21-hydroxylase deficiency and 11 beta-hydroxylase deficiency, respectively. To evaluate for the presence of 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) deficiency, the patients were classified on the basis of their 60-min delta 5-17-hydroxypregnenolone/17-OHP (delta 5-17P/17-OHP) ratio [PP1 (n = 13), less than or equal to 2 SD of Tanner I controls; PP2 (n = 17), greater than 2 SD above Tanner I controls and less than or equal to 2 SD Tanner II controls; and PP3 (n = 4), greater than 2 SD above Tanner II controls; 2.1 +/- 1.0, 6.1 +/- 1.7, and 16.1 +/- 3.3 for PP1, PP2, and PP3, respectively. delta 5-17P/17-OHP for PP1 vs. PP2, PP2 vs. PP3, and PP1 vs. PP3 were significantly different (P less than 0.05) by analysis of variance and multiple comparison testing using the Student-Newman-Keuls procedure. The four patients in PP3 were considered to have a possible nonclassical 3 beta-HSD deficiency. This diagnosis was supported by the fact that these patients had the greatest increment in delta 5-17P and dehydroepiandrosterone (DHEA) levels as well as the highest stimulated delta 5-17P/cortisol (delta 5-17P/F) ratio among the patient groups. In contrast to the ACTH-stimulated androgens there were no differences in the baseline delta 5-17P/170HP or androgens among the patient groups. Additionally, the 60-min delta 5-17P/17-OHP within the patient groups was highly correlated with the 60 min-values for delta 5-17P, DHEA, DHEA/delta 4-androstendione, and delta 5-17P/F. In the children with PP the mean bone age/chronological age (BA/CA) was 1.27 +/- .27, the mean BA/height age (BA/HA) was 1.09 +/- 0.25, and the mean HA/CA was 1.18 +/- 0.17. No differences were noted between the patient population groups in mean BA/CA, mean BA/HA, or mean HA/CA.(ABSTRACT TRUNCATED AT 400 WORDS)

Origin of an ovarian steroid cell tumor causing isosexual pseudoprecocious puberty demonstrated by the expression of adrenal steroidogenic enzymes and adrenocorticotropin receptor.

Ovarian steroid cell tumors are rare neoplasms composed of typical steroid hormone-secreting cells. Most ovarian steroid cell tumors, however, cannot be appropriately classified on a morphological basis, because the neoplastic cells closely resemble adrenal cortical cells. Nevertheless, the true adrenal origin of such tumors has been difficult to demonstrate. Here we report a 3-yr-old girl with isosexual pseudoprecocious puberty due to an ovarian steroid tumor whose adrenal cell origin was determined by the presence of messenger ribonucleic acid (mRNA) of adrenal-specific steroidogenic P450 enzymes (P450c11 and P450c21) and ACTH receptor (ACTHR). Her height was +2.3 SD, and she had Tanner stage III breast development, Tanner stage II pubic hair, and a normal clitoris. Bone age was 5 yr. Basal gonadotropin levels were undetectable (<0.6 U/L for LH and <1.0 U/L for FSH) and remained undetectable after stimulation with 100 microg GnRH, i.v. Basal serum testosterone and 17-hydroxyprogesterone levels were slightly elevated, whereas basal serum androstenedione, estradiol, and dehydroepiandrosterone sulfate levels were clearly elevated. Pelvic ultrasound disclosed an enlarged uterus and an adnexal multicystic mass in the right ovary, and pathological studies disclosed an ovarian steroid cell tumor. To establish the cellular origin of the tumor we determined the presence of mRNA for P450c11, P450c21, and ACTHR in tumor tissue and normal adrenal and ovarian tissue. Detection of ACTHR, P450c21, and P450c11 mRNAs isoforms was achieved in tumoral and adrenal control tissue, but not in the ovary control tissue. The RT-PCR products of P450c11 from adrenal control tissue were composed by both BglI-sensitive and -resistant complementary DNAs, indicating the presence of both P450c11AS and P450c11beta, whereas RT-PCR product from the tumor was resistant to BglI digestion, indicating only the presence of P450c11beta. We conclude that the histological origin of so-called adrenal rest tumor could be reliably determined by assessing the expression of specific genes in the tumor as P450c11beta and P450c21. The use ofthese molecular tools will allow a more precise classification of an important subset of the ovarian steroid cell tumors and can help to identify ectopic adrenal tissue in ovary and testis.

Aromatase p450 expression in a feminizing adrenal adenoma presenting as isosexual precocious puberty.

A 7-yr-old girl presented with isosexual precocious puberty secondary to a feminizing adrenal adenoma. The adrenal tumor was found to express aromatase messenger ribonucleic acid. Enzyme kinetic studies revealed a high level of aromatase activity in the adrenal tumor, with a K(m) of 45 nmol/L and a maximum velocity of 25.6 pmol/mg.h. Aromatase activity was approximately 500-fold higher in the tumor than in adjacent normal adrenal tissue. Although histopathological examination of the tumor was most consistent with a benign adenoma, the aromatase transcripts present in the tumor corresponded to those previously associated with malignant as well as benign tumors. We consider the pattern of aromatase expression sufficient to warrant continued follow-up for tumor recurrence. Our case demonstrates that isosexual precocious puberty secondary to a feminizing adrenal tumor can be due to estrogen synthesis from the tumor itself rather than peripheral aromatization as had been previously theorized.

Mutation in 3 beta-hydroxysteroid dehydrogenase type II associated with pseudohermaphroditism in males and premature pubarche or cryptic expression in females.

A mutation (A82T) is described in the coding sequence of the gene for 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) type II that is associated with variable clinical consequences. Four homozygotes are described, all of which showed elevated levels of delta 5 steroids consistent with 3 beta-HSD deficiency. Two males from a consanguineous family were found to be homozygous for A82T and were affected with pseudohermaphroditism. They differed in their degree of mild salt loss. In the same family a female was found to be homozygous for A82T, but was clinically normal and had no history of premature pubarche or of abnormal menstrual cycles. However, in an apparently unrelated family, the A82T mutation was found in a female affected with premature pubarche. This is the first report of a proven mutation in 3 beta-HSD type II associated with premature pubarche.

Decreased hypothalamic aromatization in female rats of true precocious puberty.

The true precocious puberty animal model induced by the single dose of danazol was used for investigating the expressions of hypothalamic aromatase in the advanced onset of puberty in rats. The day of vaginal opening and first estrus showed significant advancement in the model rats compared with the normal and vehicle rats (P < 0.01, respectively). The hypothalamic gonadotropin-releasing hormone (GnRH) mRNA expression increased significantly in the model rats compared with that in the normal and vehicle ones (P < 0.01). The levels of aromatase mRNA and protein expressions detected by RT-PCR and Western blot both decreased in the model rats compared with those in the normal and vehicle groups (P < 0.05). The results suggested that the hypothalamic aromatization might diminish in the onset of true precocious puberty of female rats.