1. Chapter 12 Effects of the Menstrual Cycle on the Acquisition of Peak Bone Mass Mimi Zumwalt, MD

2. Learning Objectives Learn about the reproductive anatomy and physiology of the normal menstrual cycleLearn about the reproductive anatomy and physiology of the normal menstrual cycle Delineate the constituents/function of bone, its biochemistry, physiology, and metabolismDelineate the constituents/function of bone, its biochemistry, physiology, and metabolism Understand the interaction between female sex hormones and components of boneUnderstand the interaction between female sex hormones and components of bone Recognize the importance of peak bone mass achievement, its definition, and methods of optimal attainmentRecognize the importance of peak bone mass achievement, its definition, and methods of optimal attainment Comprehend the effects of abnormal menses on peak bone mass, bone density, how to minimize bone loss and enhance bone gainComprehend the effects of abnormal menses on peak bone mass, bone density, how to minimize bone loss and enhance bone gain

3. Introduction Skeleton provides structural support for bodySkeleton provides structural support for body Bone is dynamic tissueBone is dynamic tissue Maximizing bone building important in growing yearsMaximizing bone building important in growing years Better to have higher peak bone mass to protect against later bone lossBetter to have higher peak bone mass to protect against later bone loss

4. Female Sex Organ Anatomy & Menstrual Cycle Physiology Uterus, ovaries, & accessory organsUterus, ovaries, & accessory organs Eggs & sex hormone productionEggs & sex hormone production Estrogen & progesteroneEstrogen & progesterone Hypothalamic-pituitary-ovarian (HPO) axisHypothalamic-pituitary-ovarian (HPO) axis GnRH, FSH, LHGnRH, FSH, LH Monthly menstrual cycleMonthly menstrual cycle Follicular, ovulatory, & luteal phasesFollicular, ovulatory, & luteal phases

5. Female Sex Hormones & Bone EstrogenEstrogen “Set point” for bone mass“Set point” for bone mass Coupling effectCoupling effect Long bone longitudinal growthLong bone longitudinal growth ProgesteroneProgesterone Synergistic w/estrogen on boneSynergistic w/estrogen on bone

6. Bone Composition, Physiology, Function & Interaction w/Ovarian Hormones Bone cells osteoblasts & osteoclastsBone cells osteoblasts & osteoclasts Formation coupled w/resorptionFormation coupled w/resorption ~99% of body’s calcium in bone~99% of body’s calcium in bone Needs vitamin D for absorptionNeeds vitamin D for absorption Estrogen essential as wellEstrogen essential as well Menstrual irregularity affects bone loss from not enough hormonal influenceMenstrual irregularity affects bone loss from not enough hormonal influence

7. Peak Bone Mass PBM mostly achieved during teenage years, especially around “adolescent growth spurt”PBM mostly achieved during teenage years, especially around “adolescent growth spurt” Maximum ~mid-twentiesMaximum ~mid-twenties 0.3% loss per year after until mid-forties0.3% loss per year after until mid-forties Genetics & environmental influenceGenetics & environmental influence Nutrition, mechanical loading thru exercise, hormonal milieu/mensesNutrition, mechanical loading thru exercise, hormonal milieu/menses 2% loss/yr if not balanced2% loss/yr if not balanced

8. Abnormal/Absent Menstrual Cycle & Peak Bone Mass Secondary amenorrheaSecondary amenorrhea Pregnancy, endocrine, anatomic, tumorsPregnancy, endocrine, anatomic, tumors Female athlete triadFemale athlete triad Premature osteoporosisPremature osteoporosis Gymnastics only partial offsetGymnastics only partial offset Gynecologist consultGynecologist consult DEXA “gold standard”DEXA “gold standard” Serum & urine markers of bone metabolismSerum & urine markers of bone metabolism

9. Conclusion Maximizing PBM essential especially during adolescent growth spurtMaximizing PBM essential especially during adolescent growth spurt Regular menses important for building boneRegular menses important for building bone Appropriate exercise & adequate nutrition (calcium & vitamin D) pertinent as wellAppropriate exercise & adequate nutrition (calcium & vitamin D) pertinent as well High PBM helps w/bone loss later in lifeHigh PBM helps w/bone loss later in life

10. Case Study You are a primary care sports medicine physician in a multi-specialty group practice consisting of pediatrics, internal medicine, OB/GYN, and family physicians. For the past few years, you have been the team physician for local high school athletes, including track and field events and other court sports. Lately, the team athletic trainer has brought in a few of the female long distance runners with similar complaints of vague, aching pain in their feet and legs, especially after a couple of weeks’ practice, e.g., running around the track. Upon further questioning, these female athletes also reveal that their menses have been very irregular and/or absent over the last year or so.You are a primary care sports medicine physician in a multi-specialty group practice consisting of pediatrics, internal medicine, OB/GYN, and family physicians. For the past few years, you have been the team physician for local high school athletes, including track and field events and other court sports. Lately, the team athletic trainer has brought in a few of the female long distance runners with similar complaints of vague, aching pain in their feet and legs, especially after a couple of weeks’ practice, e.g., running around the track. Upon further questioning, these female athletes also reveal that their menses have been very irregular and/or absent over the last year or so.