Luteinizing hormone pulsatility is disrupted at a threshold of energy availability in regularly menstruating women.
Level 2 - randomized trial
Randomized crossover trial evaluating physiological endpoints under controlled experimental conditions.
PubMed 12519869 · doi:10.1210/jc.2002-020369
What was done
Researchers evaluated the effect of varying levels of energy availability (dietary energy intake minus exercise energy expenditure) on luteinizing hormone (LH) pulsatility in 29 regularly menstruating, habitually sedentary young women of normal body composition. During the early follicular phase, participants completed 5-day interventions with supervised exercise (15 kcal/kg lean body mass [LBM] per day at 70% aerobic capacity) and clinical formula diets to establish energy availability at 45 kcal/kg LBM/day versus 10, 20, or 30 kcal/kg LBM/day across two randomized trials separated by at least 2 months. Blood was sampled daily and every 10 minutes for 24 hours post-treatment to assess LH pulsatility, reproductive hormones, and metabolic markers.
What was found
Energy availability of 30 kcal/kg LBM/day did not significantly alter LH pulsatility (P > 0.3). Below this threshold (10 and 20 kcal/kg LBM/day), LH pulse frequency decreased and LH pulse amplitude increased (all P < 0.04). Disruption of pulsatility was more pronounced in women with short luteal phases (P < 0.01). These threshold-dependent effects mirrored shifts in plasma glucose, beta-hydroxybutyrate, growth hormone, and cortisol (simultaneously P < 0.05). Absolute hormonal and metabolic values were not provided in the abstract.
Why it matters
This study provides experimental evidence of a critical energy availability threshold (below 30 kcal/kg LBM/day) for preserving normal neuroendocrine reproductive function in women, establishing a biological basis for conditions like the female athlete triad.
Limits
The study had a small sample size (n = 29) divided across three restricted-energy arms. The intervention lasted only 5 days in sedentary women, which may not capture chronic adaptations or dynamics in highly trained athletes. Absolute numerical values for pulse characteristics and hormone levels were not reported in the abstract.
Cited by
- supports In women, high-volume exercise combined with severe caloric deficit disrupts follicle-stimulating hormone and luteinizing hormone, leading to amenorrhea and cessation of ovulation.