Endocrine Regulation of Reproduction 640
Control of Gonadotropin Secretion 644 Testosterone Derivatives in the Brain 644 Testosterone Secretion and Age 645 Endocrine Functions of the Testes 645 Spermatogenesis 646 Sertoli Cells 647 Hormonal Control of
Menstrual Cycle 659
Phases of the Menstrual Cycle: Cyclic Changes in the Ovaries 660
Exchange of Molecules Across the Placenta 672 Endocrine Functions of the Placenta 673 Pituitary-like Hormones from the
Concluding Remarks 679 Interactions 680
Summary 681 Review Activities 682 Related Websites 683
■ Pituitary Gland 299
Autocrine and Paracrine Regulation 316
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Gloria, a second-year college student, goes to the student health center complaining of amenorrhea of several months' duration. Before that, her periods had always been normal. Gloria's body weight is below average for her height, but she exhibits normal development of secondary sexual characteristics. She had been diagnosed a few years earlier as hypothyroid, and thyroxine pills were prescribed for this condition. Gloria teaches an aerobics class at a local gym, and she exercises at least an hour a day. She states that she is not taking birth control pills.
A pregnancy test is performed and is negative. Blood is drawn, and the subsequent laboratory report indicates normal thyroxine levels; in fact, all measurements are within the normal range (her blood cholesterol is even on the low side).What is the most likely cause of Gloria's condition? What should she do about it?
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