[18F]2-fluoro-2-deoxy-D-glucose positron emission tomography demonstration of estrogen negative and positive feedback on luteinizing hormone secretion in women.
BACKGROUND
Precise regulation of the neuroendocrine components of the female reproductive axis involves both negative and positive feedback of estrogen on gonadotropin secretion.


OBJECTIVE
Our objective was to determine the hypothalamic and/or pituitary sites of estrogen negative and positive feedback using neuroimaging techniques.


METHODS
A graded estrogen infusion protocol was administered at a General Clinical Research Center in an academic medical center.


METHODS
Healthy postmenopausal women (n = 11) were recruited for study.


METHODS
Serum samples were measured every 4 h. A structural magnetic resonance imaging was performed at baseline, and [(18)F]2-fluoro-2-deoxy-d-glucose ((18)FDG) positron emission tomography was performed at baseline and 24 and 72 h. FDG positron emission tomography was co-registered with magnetic resonance imaging scans, and region of interest analysis was performed.


METHODS
Serum LH and estradiol were assessed. Normalized values for glucose uptake were extracted from each region of interest for each subject at each time point.


RESULTS
A decrease in normalized (18)FDG uptake was apparent in the hypothalamus at 24 h (P < 0.02) associated with decreased LH (P < 0.0005). The increase in LH at 72 h (P < 0.0005) was associated with increased pituitary (18)FDG uptake (P < 0.02) but no change in hypothalamic uptake.


CONCLUSIONS
Changes in (18)FDG uptake as a measure of metabolic activity can be demonstrated in the hypothalamus and pituitary in association with discrete hormonal events. Results are consistent with mediation of estrogen negative feedback on LH at the hypothalamus, whereas estrogen positive feedback occurs at the pituitary with no evidence of increased hypothalamic activity in women.
Reproductive Endocrine Unit, BHX-5, Massachusetts General Hospital, 55 Fruit Street, Boston, Massachusetts 02114, USA.
William E
WE
Ottowitz
Darin D
DD
Dougherty
Alan J
AJ
Fischman
Janet E
JE
Hall
D000368:Aged; D004958:Estradiol / Q000097:blood / Q000502:physiology*; D025461:Feedback, Physiological; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007986:Luteinizing Hormone / Q000378:metabolism*; D008875:Middle Aged; D049268:Positron-Emission Tomography; D011388:Prolactin / Q000097:blood; D019275:Radiopharmaceuticals
D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18; D004958:Estradiol; D011388:Prolactin; D007986:Luteinizing Hormone