78

78 CASE 78


A 17-year-old girl visits the pediatrician because of an 8-month absence of a menses.


The patient joined a cross country team at high school 3 years ago and is training for the upcoming state championships. She has ranged between the 25th and 55th percentile for both height and weight since her second birthday but has progressively lost weight during the past 2 years. All other developmental milestones were met at an appropriate age. Both parents are of normal height and stature.



PHYSICAL EXAMINATION



VS: T 37°C, P 90/min, R 22/min, BP 100/80 mm Hg, BMI 17

PE: Physical examination reveals a well-toned female athlete with minimal subcutaneous body fat.


LABORATORY STUDIES



Pregnancy test (hCG): Negative

Radiography: Normal hypothalamus and pituitary

LH: 0.4 IU/mL (normal: 0.9 to 10.6 IU/mL)

Prolactin: 12 ng/mL (normal: < 20 ng/mL)

Injection of GnRH stimulates the release of both FSH and LH.


DIAGNOSIS


Hypothalamic amenorrhea



PATHOPHYSIOLOGY OF KEY SYMPTOMS


Gonadotropin releasing hormone (GnRH) is produced and secreted by neurons in the hypothalamus and travels through the hypothalamohypophyseal portal system to the anterior pituitary to stimulate the release of follicle-stimulating hormone (FSH) and luteinizing hormone LH). The reproductive cells and glands are the targets for FSH and LH. For females, FSH stimulates ovarian follicles to mature and to release estrogen and LH stimulates the corpus luteum to secrete progesterone (Fig. 78-1).


image

FIGURE 78–1 Complex regulation of estrogen and progesterone production. FSH stimulates estrogen secretion by ovarian granulosa cells, and LH stimulates progesterone secretion by the ovary. Complex negative feedback loops inhibit both hypothalamic and anterior pituitary hormone secretion. −, negative feedback; +, positive feedback.

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Jul 4, 2016 | Posted by in PHYSIOLOGY | Comments Off on 78

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