The response of luteinizing hormone pulsatility to 5 days of low energy availability disappears by 14 years of gynecological age

Estrogen and progesterone exposure is reduced in response to energy deficiency in women aged 25-40 years

BACKGROUND

Alterations in circulating steroids are believed to be important mediators of the impact that diet and exercise have on breast cancer risk and changes in bone density. This study aimed to test the hypothesis that moderate exercise training combined with caloric restriction would produce significant menstrual disturbances and alterations in ovarian steroids in premenopausal women.

METHODS

Sedentary premenopausal women (25-40 years; body mass index: 23.6 +/- 0.6 kg/m(2)) assigned to either a light conditioning (LC, n = 9) or an exercise combined with caloric restriction group (EX + CR, n = 24) were studied for one screening, one baseline and four intervention periods equivalent to the length of subjects' menstrual cycles. Exercise consisted of supervised training sessions, i.e. two LC or four EX + CR times per week, 30-60 min at a moderate intensity. The EX + CR group was prescribed a diet representing a caloric restriction of 20-35% below baseline energy requirements, whereas the LC group remained eucaloric. Ovarian steroid exposure was determined with daily urinary estrone-1- and pregnanediol glucuronides (E1G and PdG, respectively) and mid-cycle urinary LH measures. Fitness, body composition, and serum sex hormone binding globulin (SHBG) and serum estradiol (E2) were assessed repeatedly.

RESULTS

The intervention produced significant increases in VO(2) max and decreases in both body weight (-3.7 +/- 0.5 kg; ranged from -8.8 to +1.8 kg) and percent body fat (-4.5 +/- 0.7%; ranged from -12 to +0.3%), which were attributable primarily to changes in the EX + CR subjects (time x group; P < 0.05). Serum E2 and urinary E1G and PdG concentrations declined significantly across the intervention period (time; P < 0.05), whereas SHBG increased transiently (time; P < 0.05) in the EX + CR subjects, with no significant changes observed in the LC group. The decrease in E1G area under the curve was significantly related to the daily energy deficit (R =0.61; P = 0.003), not the amount of weight lost. There was no significant impact of the intervention on menstrual cyclicity or the incidence of menstrual disturbances in either group.

CONCLUSIONS

A moderate aerobic exercise training program combined with modest weight loss in accordance with recommended guidelines produces significant reductions in ovarian steroid exposure without disrupting menstrual cyclicity in premenopausal women aged 25-40 years. Exposure to a daily energy deficit is a stronger predictor of the decline in estrogen exposure than decreases in body weight.

The female athlete triad: components, nutrition issues, and health consequences

This paper, which was part of the International Association of Athletics Federations (IAAF) 2007 Nutritional Consensus Conference, briefly reviews the components of the female athlete triad (Triad): energy availability, menstrual status, and bone health. Each component of the Triad spans a continuum from health to disease, and female athletes can have symptoms related to each component of the Triad to different degrees. Low energy availability is the primary factor that impairs menstrual dysfunction and bone health in the Triad. We discuss nutritional issues associated with the Triad, focusing on intakes of macronutrients needed for good health, and stress fractures, the most common injury associated with the Triad. Finally, we briefly discuss screening and treatment for the Triad and the occurrence of the Triad in men.

Bone density in the adolescent athlete

Adolescence is a critical time for bone mass accrual, and increases in bone mass through puberty are dependent on rising levels of gonadal steroids, growth hormone and insulin like growth factor-1. Many high school girls are involved in athletic activities, and as many as 23.5% of adolescent athletes have been reported to develop amenorrhea. This review focuses on (1) factors that determine which athletes are likely to develop amenorrhea, such as a negative energy balance state, low levels of leptin and high levels of ghrelin, and (2) the impact of hypogonadism in athletes on bone metabolism. Beneficial effects of increased mechanical loading from athletic activity do not appear to protect against the deleterious effects of hypogonadism in adolescent athletes.

Bone metabolism in adolescent athletes with amenorrhea, athletes with eumenorrhea, and control subjects

OBJECTIVE

We hypothesized that, despite increased activity, bone density would be low in athletes with amenorrhea, compared with athletes with eumenorrhea and control subjects, because of associated hypogonadism and would be associated with a decrease in bone formation and increases in bone-resorption markers.

METHODS

In a cross-sectional study, we examined bone-density measures (spine, hip, and whole body) and body composition by using dual-energy radiograph absorptiometry and assessed fasting levels of insulin-like growth factor I and bone-turnover markers (N-terminal propeptied of type 1 procollagen and N-telopeptide) in 21 athletes with amenorrhea, 18 athletes with eumenorrhea, and 18 control subjects. Subjects were 12 to 18 years of age and of comparable chronologic and bone age.

RESULTS

Athletes with amenorrhea had lower bone-density z scores at the spine and whole body, compared with athletes with eumenorrhea and control subjects, and lower hip z scores, compared with athletes with eumenorrhea. Lean mass did not differ between groups. However, athletes with amenorrhea had lower BMI z scores than did athletes with eumenorrhea and lower insulin-like growth factor I levels than did control subjects. Levels of both markers of bone turnover were lower in athletes with amenorrhea than in control subjects. BMI z scores, lean mass, insulin-like growth factor I levels, and diagnostic category were important independent predictors of bone mineral density z scores.

CONCLUSIONS

Although they showed no significant differences in lean mass, compared with athletes with eumenorrhea and control subjects, athletes with amenorrhea had lower bone density at the spine and whole body. Insulin-like growth factor I levels, body-composition parameters, and menstrual status were important predictors of bone density. Follow-up studies are necessary to determine whether amenorrhea in athletes adversely affects the rate of bone mass accrual and therefore peak bone mass.

Energy availability and infertility

PURPOSE OF REVIEW

To relate recent research on the dependence of reproductive function on energy availability in women to recent clinical experience in the treatment of anorexia nervosa.

RECENT FINDINGS

The dependence of luteinizing hormone pulsatility on energy availability declines during adolescence, but the responses of leptin and other peripheral signals of energy deficiency do not. This finding suggests that central sensitivity to these signals may decline during adolescence. Energy availability may be inadequate in anorexia nervosa patients whose menstrual cycles are not restored after weight recovery.

SUMMARY

Energy availability is a theoretically satisfying and operationally controllable concept for understanding, investigating, and managing the energy dependence of reproductive function. Nutritional intervention to restore menstrual cycles in anorexia nervosa patients might be more successful if it was guided by energy availability and ovarian volume rather than energy intake and body weight.

Polymorphism in the insulin-like growth factor 1 gene is associated with age at menarche in caucasian females

BACKGROUND

The insulin-like growth factor 1 (IGF1) gene, which plays a crucial role in hypothalamic-pituitary-ovarian hormone-controlled metabolic processes, may influence the onset of menarche. Our study aimed to test association between IGF1 polymorphisms with the variation of age at menarche (AAM) in Caucasian females.

METHODS

We recruited a sample of 1048 females from 354 Caucasian nuclear families and genotyped 19 single-nucleotide polymorphisms (SNPs) spanning the entire IGF1 gene. Pairwise linkage disequilibrium among SNPs was measured, and the haplotype blocks were inferred. Both single SNP markers and haplotypes were tested for association with AAM using the quantitative transmission disequilibrium test.

RESULTS

Significant association (P = 0.0153) between AAM and SNP3 (rs6214) in block1 was detected.

CONCLUSIONS

Our results suggested a potential effect of SNP3 in the IGF1 gene on AAM variation in Caucasian women for the first time. However, further independent studies are needed to confirm our findings.

Astressin B, a corticotropin-releasing hormone receptor antagonist, accelerates the return to normal luteal function after an inflammatory-like stress challenge in the rhesus monkey

Endogenous release of CRH in stress has been associated with a dysfunctional reproductive endocrine axis. In the rhesus monkey, an inflammatory-like stress challenge in the luteal phase decreases luteal secretory function. Here, we tested the effectiveness of astressin B, a nonspecific CRH receptor antagonist, in constraining the deleterious impact of a 10-d lipopolysaccharide (LPS) challenge on the menstrual cycle. Two protocols were carried out in nine animals. In the first, the animals, after showing two normal consecutive control cycles, were injected daily for 10 days with LPS (75-125 mug/d) during the luteal phase of the cycle. The animals were followed through the two postchallenge cycles. The second protocol, carried out in the following year, was identical with protocol 1, except that the animals were treated with astressin B (0.45 mg/kg) 1 h before each daily LPS challenge during the luteal phase. Blood samples were obtained daily to document cyclic hormones levels. The LPS challenge significantly decreased luteal progesterone and LH release during the challenge cycle. Inhibition of luteal progesterone extended to the two successive postchallenge cycles. Astressin B treatment prevented luteal LH but not luteal progesterone decrease during the treatment cycle and restored normal progesterone secretion during the two posttreatment cycles. We conclude that the deleterious impact of a short-term inflammatory stress challenge on luteal function is far longer than the stress period itself. Systemic administration of astressin B accelerates the return to normal luteal function, presumably by restoring normal neuroendocrine regulation of gonadotropin secretion.