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PubMed2002

National estimates of the timing of sexual maturation and racial differences among US children.

OBJECTIVE: To provide clinically meaningful, normative reference data that describe the timing of sexual maturity indicators among a national sample of US children and to determine the degree of racial/ethnic differences in these estimates for each maturity indicator. METHODS: Tanner staging assessment of sexual maturity indicators was recorded from 4263 non-Hispanic white, black, and Mexican American girls and boys aged 8.00 to 19.00 years as part of the Third National Health and Nutrition Examination Survey (NHANES III) conducted between 1988 and 1994. NHANES III followed a complex, stratified, multistage probability cluster design. SUDAAN was used to calculate the mean age and standard error for each maturity stage and the proportion of entry into a maturity stage and to incorporate the sampling weight and design effects of the NHANES III complex sampling design. Probit analysis and median age at entry into a maturity stage and its fiducial limits were calculated using SAS 8.2. RESULTS: Reference data for age at entry for maturity stages are presented in tabular and graphical format. Non-Hispanic black girls had an earlier sexual development for pubic hair and breast development either by median age at entry for a stage or for the mean age for a stage than Mexican American or non-Hispanic white girls. There were few to no significant differences between the Mexican American and non-Hispanic white girls. Non-Hispanic black boys also had earlier median and mean ages for sexual maturity stages than the non-Hispanic white and Mexican American boys. CONCLUSION: Non-Hispanic black girls and boys mature early, but US children completed their sexual development at approximately the same ages. The present reference data for the timing of sexual maturation are recommended for the interpretation of assessments of sexual maturity in US children.

Adolescent↗

PubMed1995

Validity of self-assessment of sexual maturation in adolescent male patients with cystic fibrosis.

PURPOSE: Self-assessment of sexual maturity by healthy male adolescents has been found to correlate closely with physician ratings. Data are lacking, however, in adolescents with cystic fibrosis (CF), where an altered body image may affect self-assessment. Delayed sexual maturation occurs in many patients with CF, particularly those with severe disease. We hypothesized that self-assessment of sexual maturation by adolescents with CF would agree with physician ratings. METHODS: Using Tanner's standard photographs for pubic hair (PH) and genital (G) development, we compared self-assessment of sexual maturation to physician rating in 34 adolescent male patients with CF and 27 healthy male controls (C). RESULTS: The two groups did not differ in age. All subjects were initially examined and Tanner-staged by a physician (SRB), and instructed in self-assessment using the Tanner photographs; they then performed a self-assessment. Scores by physician and subjects were assessed for inter-observer agreement by Kappa analysis. For the CF group, 29 of 34 PH assessments and 21 of 34 G assessments demonstrated exact inter-observer agreement between physician and subject ratings. The Kappa coefficient, kappa, (weighted for the degree of closeness between two observers) was 0.946 for PH and 0.840 for G and the C group, kappa was 0.905 for PH and 0.737 for G. Repeat analysis combining stages 3 and 4 PH and G development yielded higher inter-observer agreement in the CF group (33 of 34 PH assessments and 26 of 34 G assessments) and in the C group (24 of 27 PH assessments and 18 of 27 G assessments). CONCLUSIONS: Self-assessment is a valid method to assess sexual maturity in clinical evaluation and as a research tool in the study of patients with CF.

Adolescent↗

PubMed1984

Daily afternoon administration of melatonin does not irreversibly inhibit sexual maturation in the male rat.

Previous studies from our laboratory demonstrated that daily afternoon melatonin injections from 20-40 days of age inhibited sexual development of young male rats, whereas in adult animals, similar injections had no effect. The present study was designed to determine more precisely the critical age period during which melatonin exerts its inhibiting effect and to see whether spontaneous sexual maturation resumes after discontinuation of melatonin administration at 45 days of age or even during continuous administration of melatonin until 115 days of age. Sexual maturation was evaluated using weights of seminal vesicles and testes; plasma levels of testosterone, FSH, and LH; pituitary contents and concentrations of FSH and LH; and, finally, pituitary content of GnRH receptors. Administration of melatonin to young male rats from 20-30 days of life had the same inhibitory effect on sexual maturation at 40 days as melatonin injections from 20-40 days. In contrast, administration of melatonin from 30-40 days only slightly decreased plasma testosterone concentration, weight of seminal vesicles, and pituitary GnRH receptor content. Melatonin administration from 38-40 days had no effect. Daily melatonin administration from 20-45 days of age was followed by resumption of sexual maturation, as observed at 70 days. The recovery was complete by 80 days of age when all of the parameters studied reflected complete sexual maturation. Finally, in rats treated continuously with melatonin from days 20 until 115, sexual maturation occurred but was delayed by about 20-30 days. Beginning of sexual development was observed at 60 days of life, and full development was attained only at 100 days. These data confirm that melatonin delays sexual maturation in the young male rat when administered daily in the afternoon. They demonstrate that this inhibitory action of melatonin is most critical between 20 and 30 days of life and is reversible regardless of whether melatonin administration is discontinued after 45 days of life. The suppression of the pubertal peaks of pituitary GnRH receptor number and pituitary and plasma FSH concentrations in treated rats suggests that melatonin interferes with the pubertal increase in GnRH secretion. In conclusion, these reversible effects of melatonin suggest that this pineal indolamine represents an important factor for the timing of sexual maturation.

Aging↗

PubMedDate not supplied

Neonatal encephalopathy: an indicator of early sexual maturation in girls.

Of 161 girls with neonatal encephalopathy who were prospectively assessed until 8 years of age, 7 (4.3%) demonstrated variable degrees of early sexual maturation. This finding was significantly greater than the accepted 0.6%, estimated for the general population. Four of the 7 girls with early sexual maturation had physical disabilities (i.e., 3 with cerebral palsy, 1 neurosensory deafness) which indicated that 10% of the 40 physically disabled girls had early sexual maturation. Three (2.5%) of 121 girls without physical disabilities matured early. Sexual maturation began 5 years or longer after the diagnosis of neonatal encephalopathy. An increased incidence of early sexual maturation in girls with neonatal encephalopathy indicates the importance of long-term follow-up of this population. This study provides an indication of a link between newborn illnesses causing neonatal encephalopathy and early sexual maturation in girls without progressive, structural, intracranial pathology and suggests further study of some girls previously diagnosed as having idiopathic precocious puberty.

Asphyxia Neonatorum↗

PubMed1998

Hormonal responses to exercise in girls during sexual maturation.

The dependence of hormonal responses to exercise on sexual maturation was tested in three-year longitudinal experiment on 34 girls (11-12 years old at the beginning of the study). Sexual maturation of the girls was evaluated using Tanner scale. Girls were divided into three groups: maturation stages 1-2, 2-4 and 4-5. Children performed a 20-min cycle exercise at 60% of maximal oxygen uptake (VO max) once a year. Cortisol, insulin, somatotropin, beta-estradiol, progesterone and testosterone were determined in venous blood by RIA procedures. High basal levels of beta-estradiol and somatotropin appeared in stages 2-4 (387 +/- 92 pmol.l-1) and 12.9 +/- 2.85 ng.ml-1, respectively) and 4-5 (358 +/- 54 pmol.l-1) and 14.3 +/- 1.53 ng.ml-1, respectively). The basal progesterone level increased with maturation, testosterone appeared in the blood in stages 2-4 and 4-5. The exercise resulted in increased levels of cortisol and somatotropin, and a drop in insulin in all girls. The cortisol response was most pronounced in stage 1-2. Postexercise insulin concentration was the highest in stage 4-5. beta-estradiol level increased by 23% in stages 1-2 and 4-5, while the response was insignificant in stages 2-4. Exercise-induced progesterone increase was significant in stage 4-5. In conclusion, sexual maturation associates with several quantitative changes in exercise-induced hormonal responses.

Child↗

PubMed1984

[Growth and sexual maturation of the male house musk shrew (Suncus murinus)].

The sexual maturation in the male house musk shrew, Suncus murinus, was investigated by weighing gonads, accessory sexual organs and various other organs, and measuring testosterone concentrations in the plasma from birth to 50 days of age. The histological and histochemical studies of the testis were also carried out. Testicular weight increased markedly from 10 days of age. On 15 days of age, the activity of delta 5-3 beta-Hydroxysteroid dehydrogenase (HSD) was detected in Leydig cells. In accordance with an increase of HSD activity, the concentrations of plasma testosterone raised rapidly from 15 days of age and reached a peak on Day 30. Growth of prostate glands and seminal vesicles showed a sigmoidal pattern and their significant growth began from Day 25. Sperms were detected first in the seminiferous tubules on Day 28, and most tubules were filled with many sperms on Day 33. From these results, the beginning of sexual maturation, i.e. puberty, of the male shrew is considered to be around Day 25. The weight gain of testes, accessory sexual organs and the body became slower on Day 40. The male animal of Day 40 could mate and impregnate the female. Therefore, the male shrew seems to attain to the sexual maturity between days 35 and 40.

Age Factors↗

PubMedDate not supplied

Concentrations of free testosterone, total testosterone, and androgen binding protein in the peripheral serum of male rats during sexual maturation.

To investigate the relationship between free testosterone and sexual maturation in the male rat, animals were decapitated every 5 days from 25 through 75 days of life. Serum was assayed for androgen binding protein and total testosterone by radioimmunoassay. Free testosterone concentrations were calculated from the total testosterone concentration and the free testosterone fraction. The free testosterone fraction was determined by ultrafiltration. The pubertal increase in relative prostate and relative seminal vesicle weights began between 45 and 50 days and 40 and 45 days, respectively. Although the over-all trend in the free testosterone fraction was to increase with increasing age (r = 0.46, P less than 0.0001), there was a significant secondary peak at 50 days. The serum concentration of androgen binding protein was highest on day 25, fell rapidly until day 40, and declined slowly thereafter. Despite these variations in both androgen binding protein and the free testosterone fraction during sexual maturation, the calculated serum concentration of free testosterone was remarkably similar in pattern to that of total testosterone (r = 0.99, P less than 0.0001). These data indicate that the serum concentration of total testosterone is an accurate reflection of the serum concentration of free testosterone during the sexual maturation of the male rat.

Aging↗

PubMed1985

[Serum hormone level and Kupperman menopausal complaints in sexually mature women with disturbance of ovulation].

In 103 sexually mature women with disturbance of ovulation, a possible relationship between Kupperman menopausal complaints and endocrinological status was investigated to find the cause of climacteric syndrome. The Kupperman index was increased as the disturbance of ovulation was advanced from the stage of anovulatory cycle to amenorrhea I and further to amenorrhea II. In parallel with the advance in disturbance of ovulation, serum FSH and LH levels rose significantly, and serum estrone (E1) and estradiol (E2) levels dropped. Prolactin (PRL) showed a tendency to decrease. There were some hormonal patterns characteristic of individual complaints; hot flush was associated with increased FSH and LH, and decreased E1 and E2; difficulty in falling asleep, excitability, and fatigability, with increased FSH and LH, and decreased E2; nervousness, with increased LH and decreased E2; headache, with increased LH and PRL, and decreased E2; feeling of cold, with decreased E2 and PRL; and numbness and shoulder stiffness, with decreased E2. In sexually mature women, the complaints associated with abnormal levels of two or more kinds of hormones seemed to be most specifically related with decreased E2, followed by increased LH. Fatigability and headache developed specifically in the ovulatory phase of women with normal menstrual cycles (105 subjects), suggesting that these two complaints are closely related to increased LH. These results indicate that the majority of Kupperman menopausal complaints have their individually specific endocrinological cause, and that they may develop even in sexually mature women if those specific conditions exist. In climacteric syndrome in a narrow sense (i.e., dysautonomic type), each complaint may also have its specific endocrinological cause.

Adult↗

PubMed1989

Geographic differences for delay of sexual maturation in Peromyscus leucopus: effects of photoperiod, pinealectomy, and melatonin.

Effects of short-day photoperiod, pinealectomy, and melatonin on sexual maturation were tested in Peromyscus leucopus from either Connecticut (CT) or Georgia (GA). Laboratory reared-stocks from CT and GA were exposed to short daylength (photoperiod) from birth or 25 days of age. At 12 wk of age, delay in sexual maturation was indicated in most CT mice by decreased testis length, combined testes weight, and seminal vesicle weight. Conversely, GA animals did not delay sexual maturation when exposed to short-day photoperiod from either birth or 25 days of age. These results indicate that responses to short daylengths differ for juvenile CT and GA populations. In a second experiment, pinealectomized or sham-operated CT males were exposed to short-day (9L:15D) or long-day (16L:8D) photoperiod from birth. Pinealectomy blocked the effect of short daylength on reproduction. Therefore, the pineal must be involved in the delay of sexual maturation observed for short-day CT mice. The effects of melatonin, a pineal gland hormone, were tested with chronic s.c. implants or daily injections. In CT mice given either melatonin implants or afternoon injections, sexual maturation was delayed. GA mice were insensitive to all melatonin treatments. Further, no differences in circadian organization (phase angle, duration of activity, period under constant dark) between GA and CT animals were apparent. Collectively, these studies indicate that melatonin is involved in the mechanism responsible for delay of sexual maturation in CT mice. Short-day insensitivity of GA Peromyscus leucopus probably results from a deficiency in the melatonin effector pathway and is not due to a disruption of circadian organization.

Animals↗

PubMed1986

Body composition and other physical parameters as determinants of age at sexual maturity and performance efficiency in dwarf hens divergently selected for body weight.

Hens in this study were produced from random breeding within lines (high, low, and control) of dwarf White Leghorns that had been divergently selected for four generations for 20-week body weight. Birds were weighed at 10 weeks of age and placed in individual cages at 18 weeks of age. Body weights, shank lengths, and egg weights were obtained at sexual maturity (day of first egg) and at 4, 8, 12, and 16 weeks after sexual maturity. Egg production was recorded during 28-day periods. Thirty hens/line were sampled at sexual maturity and at the above times after sexual maturity for body composition (percent fat, protein, moisture, and ash). High line hens showed increased percent body fat and reduced percent protein and moisture compared to low and control hens. Coefficients of determination (R2) for age at sexual maturity and body weight were small (R2 less than or equal to .20) for high and control hens. There were no meaningful relationships between body weight or other physical measurements and sexual maturity in low hens. There were no significant relationships between body composition and age at sexual maturity in high and control hens. There was a strong cubic association (R2 = .73; P less than .001) between percent ash and age at sexual maturity in low hens, although the biological importance of this relationship was uncertain. Coefficients of determination between body weight and performance efficiency (egg mass per body weight) were small to moderate (R2 = .04 to .46) for high and control hens.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗

PubMed2002

Methods for predicting sexual maturity in male cynomolgus macaques on the basis of age, body weight, and histologic evaluation of the testes.

In pharmaceutical drug safety testing, sexual maturity is an important experimental parameter. Histologic immaturity of the tissues of the reproductive system can interfere with the interpretation of compound-related effects on the reproductive organs. In female cynomolgus macaques, determination of sexual maturity is simplified by the presence of a menstrual cycle. For male cynomolgus macaques, predicting maturity is much more difficult. In this study, we evaluated methods that would reliably predict sexual maturity in male cynomolgus macaques. The results of histologic examination of testes of control male cynomolgus macaques used for drug safety studies were examined retrospectively for evidence of sexual maturity. These data were compared with age and body weight determinations to establish statistical models for determining the probability that a male cynomolgus macaque is sexually mature. This model presents a simple prospective method of predicting sexual maturity in male cynomolgus macaques.

Aging↗

PubMed1979

Effects of zinc deficiency upon pituitary function in sexually mature and immature male rats.

Serum pituitary levels of growth hormone (GH), thyrotropin (TSH), prolactin (PRL), luteinizing hormone (LH) and follicle stimulating hormone (FSH) were measured in sexually mature (adult) and sexually immature (juvenile) male rats who had been deprived of dietary zinc for 15 and 7 weeks, respectively. When compared to pair-fed control rats receiving a zinc supplemented diet, both the adult and juvenile zinc deficient rats had significantly lower body weights, tail lengths and ventral prostate weights. The testes of the sexually immature rats were also smaller than those of the pair-fed animals. In sexually mature, zinc deficient rats serum concentrations of GH and testosterone were significantly lower and serum LH levels significantly higher than in ad libitum fed control rats. Pituitary and hypothalamic levels of other hormones did not differ from values recorded in control animals. In sexually immature zinc deficient rats serum concentrations of GH were also significantly depressed; pituitary content and concentration of LH and pituitary and serum levels of FSH were significantly increased over control values. No discernible effects of zinc deficiency upon hyplthalamic content of LH-releasing hormone or serum concentrations of PRL or TSH were recorded in juvenile rats. Zinc deficiency has minimal effects upon the hypothalamic-pituitary axis of sexually mature rats. In sexually immature males, zinc deprivation leads to impairment of gonadal growth and increased synthesis and/or secretion of the pituitary gonadotropins.

Aging↗

PubMed1998

Rearing with males accelerates onset of sexual maturity in female domestic fowl.

Two experiments were conducted to investigate the effects of male presence on sexual maturation and sexual responses toward humans in laying strain females. In Experiment 1, two flocks of 50 medium-hybrid females were reared without males (separate-sex) and two flocks with males (mixed-sex) from 1 d of age. Mixed-sex females came into lay sooner and laid more eggs up to 22 wk of age than separate-sex females (P < 0.05). Comb size was also greater in mixed-sex females at 15 and 20 wk of age (P < 0.05). In Experiment 2, six replicate groups per treatment with n = 10 females per group were reared in separate-sex, mixed-sex, or adjacent to mixed-sex groups. Rearing adjacent to mixed-sex groups, which allowed visual and auditory contact with males, was just as effective for accelerating sexual maturation as was rearing in mixed-sex groups. Females reared in and adjacent to mixed-sex groups began to lay earlier (P < 0.05) and had larger combs (P < 0.05) than separate-sex females. However, after 22 wk of age, egg production rates of separate-sex females surpassed those of mixed-sex and adjacent females, resulting in similar numbers of eggs produced through 30 wk of age (P > 0.10). During tests for sexual responsiveness to humans, over 80% of females in separate-sex and adjacent to mixed-sex groups assumed a sexual crouch, whereas less than 20% of females in mixed-sex groups crouched (P < 0.001, chi-square). The degree of contact with males during rearing affected the females' physiological measures of reproductive function differently than behavioral measures.

Age Factors↗

PubMed2005

Characterization of male killer whale (Orcinus orca) sexual maturation and reproductive seasonality.

Longitudinal serum testosterone concentrations (n=10 males) and semen production (n=2 males) in killer whales were evaluated to: (1) characterize fluctuations in serum testosterone concentrations with respect to reproductive maturity and season; (2) compare morphologic changes to estimated age of sexual maturity, based on changes in serum testosterone concentrations; and (3) evaluate seasonal changes in sperm production. Classification of reproductive status and age class was based on differences (P < 0.05) in serum testosterone concentrations according to age; juvenile males ranged from 1 to 7 years (mean+/-S.D. testosterone, 0.13+/-0.20 ng/mL), pubertal males from 8 to 12 years (2.88+/-3.20 ng/mL), and sexually mature animals were 13 years and older (5.57+/-2.90 ng/mL). For captive-born males, serum testosterone concentrations, total body length and height to width ratio of the dorsal fin were 0.7+/-0.7 ng/mL, 495.6+/-17.5 cm and 1.14+/-0.13c m, respectively, at puberty; at sexual maturity, these end points were 6.0+/-3.3 ng/mL, 548+/-20 cm and 1.36+/-0.1cm. Serum testosterone concentrations were higher (P<0.05) from March to June than from December to February in pubertal animals (4.2+/-3.4 ng/mL versus 1.4+/-2.6 ng/mL) and than from September to December in sexually mature animals (7.2+/-3.3 ng/mL versus 4.0+/-2.0 ng/mL). Ejaculates (n = 90) collected from two males had similar (P > 0.05) sperm concentrations across all months. These data represent the first comprehensive study on male testosterone concentrations during and after sexual maturation, and on reproductive seasonality in the killer whale.

Aging↗

PubMed2001

Effects of photostimulatory light intensity on ovarian morphology and carcass traits at sexual maturity in modern and antique egg-type pullets.

The effects of light intensity during sexual maturation on ovarian and carcass morphology at first oviposition [sexual maturity (SM)] were examined in two Single Comb White Leghorn (SCWL) strains. A modern commercial layer strain (COMM; Shaver Starcross 288) and an antique randombred control strain (ANT) were used to compare the effects of changes in laying stock on their response to varying light intensities from photostimulation (PS) until SM. Two hundred pullets from each strain were reared following COMM breeder guidelines. At 18 wk of age, 32 COMM and 32 ANT pullets were individually caged in individually lit cages and photostimulated with light intensities of 1, 5, 50, and 500 lx. Each bird was processed when it reached SM, and carcass and ovarian morphology were assessed. The ANT birds came into production 9.1 d later than the COMM birds, on average. The ANT pullets consumed 7.0% more feed per day than COMM pullets but gained at a slower rate (ANT = 12.9 g/d; COMM = 15.0 g/d). The ANT birds reached SM at a greater weight and with a smaller ovary than did COMM birds. Although the number of large yellow follicles (LYF) was similar between strains (mean = 6.72), both LYF weight and first egg weight were lower in ANT birds than in COMM birds. The COMM layer strain was more growth efficient and had a greater emphasis on ovary maintenance. Light intensity had no effect on the timing of SM or on BW at SM, indicating that all intensities used were effectively able to stimulate the sexual maturation process. However, ovary weight and number of LYF exhibited an increasing dose response to light intensity, particularly in the COMM birds. Overall, the birds photostimulated with 1 lx of light had reduced ovary development and were heavier than their counterparts exposed to 50 and 500 lx. Within the ANT strain, LYF numbers were not significantly affected by light intensities, whereas, within the COMM strain, LYF numbers were 4.88, 6.63, 7.88, and 8.13 for the 1-, 5-, 50-, and 500-lx intensity groups, respectively. Although light intensity did not affect the rate of sexual maturation, it altered ovarian morphology and carcass lipid stores. A light intensity of 1 lx was limiting to ovarian follicle formation and caused increased carcass weight compared with birds on higher light intensity treatments. The COMM birds were more negatively affected by low light intensity than were the ANT birds, indicating that light intensity may be a more critical environmental factor with modern, highly efficient SCWL strains than has previously been thought. Light intensity can affect the reproductive development and likely the associated egg production potential of modern layer stocks.

Animal Husbandry↗

PubMed1998

Exercise-induced hormone responses in girls at different stages of sexual maturation.

The dependence of exercise-induced hormone responses on sexual maturation was tested in a 3-year longitudinal experiment on 34 girls (aged 11-12 years at the beginning). Sexual maturation was evaluated by Tanners five-stage scale. Children cycled for 20-min at 60% maximal oxygen uptake once a year. Cortisol, insulin, growth hormone, beta-oestradiol, progesterone and testosterone concentrations in venous blood were determined by radioimmunoassay procedures. Basal concentrations of growth hormone increased and of cortisol decreased when breast stage III was reached. Reaching breast stage IV was associated with an increase in basal concentrations of beta-oestradiol, progesterone and testosterone. The exercise induced significant increases in concentrations of cortisol, growth hormone and beta-oestradiol and a decrease in insulin concentration. At breast stage III the increase in cortisol concentration was to a lower level [467 (SEM 42) vs 567 (SEM 46)nmol x l(-1)] and growth hormone concentration to a higher level [29.4 (SEM 0.5) vs 12.8 (SEM 0.4)ng x ml(-1)], while the fall in insulin concentration was less pronounced [postexercise level 10.6 (SEM 0.9) vs 7.8 (SEM 0.8)mU x l(-1)] than in stage II. The magnitude of the cortisol response was reduced in the last stage of breast development (+42.1% vs +55.5% at stage II, +66.2% at stage III, and +50.0% at stage IV). The magnitude of beta-oestradiol response was the lowest in breast stage IV (+15.8%) and the highest at stage V (+41.1%). The progesterone response became significant at stage IV and testosterone response at stage V. In conclusion, we found that reaching breast stage III was associated with altered responses of cortisol, insulin and growth hormone concentrations while the responses of the sex hormone concentrations became pronounced in the last stages of sexual maturation.

Adolescent↗

PubMed2002

Transcription and translation of the salmon gonadotropin-releasing hormone genes in brain and gonads of sexually maturing rainbow trout (Oncorhynchus mykiss).

Rainbow trout sexually mature at the end of Year 3. The form of GnRH that controls gonadotropin release in trout is salmon GnRH (sGnRH). In the tetraploid rainbow trout, two genes encode an identical sGnRH peptide. The sGnRH gene-1 produces one mRNA, whereas sGnRH gene-2 can produce more than one. This study asks whether the transcripts and their protein products are expressed in the brain and gonads and whether the pattern correlates with sexual maturity over the final year leading to first spawning. Brain sGnRH mRNA and protein were continuously present throughout the third year. We show for the first time that the long sGnRH-2 mRNA transcript is expressed in neural tissue and not exclusively in gonadal tissue. Expression of the long sGnRH-2 mRNA in the brain coincides with high levels of sGnRH peptide in the brain during a time of increased gonadal growth. Thus, the long sGnRH-2 mRNA in the brain may act to regulate sGnRH production in a stage-specific rather than a tissue-specific manner. In gonads, local sGnRH is thought to play an autocrine/paracrine role in regulating gonadal maturation and spawning. In the maturing gonads, sGnRH gene-1 and -2 are expressed intermittently. Strikingly, sGnRH peptide was not detected in the gonads at any time during Year 3. These results suggest that either the sGnRH transcripts in the gonads are not translated into protein or, if translated, the protein is rapidly released, resulting in gonadal content below 1 fM per fish.

Alternative Splicing↗

PubMed1997

Secular trend in the sexual maturation of southern Chinese girls.

In 1993, a cross-sectional study of sexual maturation of normal Chinese schoolgirls was performed in Hong Kong. The aim of the study was to obtain an up-to-date reference for normal pubertal development in Chinese girls. Breast development was assessed in 3749 girls aged 7-19 y, and pubic hair rating was assessed in 3745 girls. Menstrual status was recorded in 6467 girls over 6 y of age. The median age of onset of puberty as indicated by breast stage II or above was 9.78 (95% CI 9.70-9.85) y. The median age of onset of pubic hair development was 11.64 (95% CI 11.56-11.72) y. The median age of menarche was 12.38 (95% CI 11.98-12.78) years. Percentile values for the age at which each puberty staging appeared were constructed and incorporated into the height-for-age charts. When comparison is made with similar studies done in 1962 and 1979, a significant downward secular trend in sexual maturation is observed (p < 0.01). Except for breast development the downward secular trend in sexual maturation appears to be diminishing and may be coming to a halt in the Chinese girls in Hong Kong. Their median ages of sexual maturation are now among one of the earliest medians recorded in the world population studied.

Adolescent↗