Final answer:
Female athletes can experience a range of menstrual disturbances due to factors like the Female Athlete Triad and conditions such as endometriosis. The secretory phase is part of the menstrual cycle after ovulation, preparing the uterus for possible pregnancy, not when menstruation occurs. Menarche signifies a girl's first menstrual period.
Step-by-step explanation:
The statement 'More than half of female athletes have menstrual dysfunction' is a broad one and the accuracy can vary based on the population being considered and the specific definition of menstrual dysfunction used. In general, female athletes can experience a range of menstrual disturbances ranging from amenorrhea (absence of menstruation) to menstrual irregularities due to what is known as the Female Athlete Triad. The Female Athlete Triad refers to a syndrome in which eating disorders (or low energy availability), amenorrhea, and decreased bone density (osteoporosis) happen together. Moreover, female athletes may also be at risk for conditions like endometriosis, where endometrial tissue grows outside the uterus, which can be caused by factors such as retrograde menstruation.
Concerning the menstrual cycle, the secretory phase is not when menstruation occurs; it is the phase following ovulation, where the uterine lining is prepared to support a potential pregnancy. The menstrual flow typically marks the beginning of the follicular phase. Menarche, another term related to menstruation, is defined as a girl's first menstrual period.