North American Registry of Midwives (NARM) Practice Exam

Which of the following is NOT a physiological effect of estrogen?

1. Maturation of ovarian follicles

2. Increased basal metabolism

3. Development of secondary sex characteristics

4. Thickening of the endometrial lining

The correct answer is: Increased basal metabolism

The physiological effects of estrogen are extensive and critical in various bodily functions, especially regarding the reproductive system. While all the listed options represent actions of estrogen, increased basal metabolism is particularly noteworthy as it is not a direct effect of estrogen. Estrogen primarily supports the maturation of ovarian follicles, fostering the growth and development necessary for ovulation. It plays a vital role in the development of secondary sex characteristics, such as breast development and the distribution of body fat typical of female physiology. Additionally, estrogen is responsible for thickening the endometrial lining, preparing the uterus for potential implantation of a fertilized egg during the menstrual cycle. Increased basal metabolism, while influenced by a range of hormones including thyroid hormones, is not a direct physiological effect specifically attributed to estrogen. While estrogen can indirectly affect metabolic rate through its actions on body composition and overall energy expenditure, it does not primarily function to increase basal metabolism. This distinction highlights why increased basal metabolism is the correct choice as something outside the direct physiological effects of estrogen.