Dieting causes menstrual irregularities in normal weight young women through impairment of episodic luteinizing hormone secretion.

Thirteen healthy, normal weight young women were studied throughout a control cycle and a diet cycle, during which they lost 1 kg per week on a vegetarian 800 kcal diet. Blood was sampled daily in the morning, and at weekly intervals, collected at 10-minute intervals for 6 hours. Follicle growth was monitored by ultrasonic measurement. All subjects showed normal cyclic gonadal function during the control cycle. Cyclic gonadal function remained unaltered in two subjects during the diet cycle. No dominant follicle developed in seven others, while another four showed apparently normal follicular development but impaired progesterone secretion by the corpus luteum. Comparison of both cycles revealed that episodic luteinizing hormone (LH) secretion during the follicular phase was altered by dieting. Average LH concentrations and the frequency of episodic secretions were significantly reduced during the follicular phase but not during the luteal phase. Follicle-stimulating hormone was unaltered.