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Dramatically increased intestinal absorption of cholesterol following hypophysectomy is normalized by thyroid hormone
Cecilia Gälman1, Ylva Bonde, Manuela Matasconi
1Karolinska Institute, Center for Endocrinology, Metabolism, and Diabetes, Department of Medicine and Molecular Nutrition Unit, Center for Nutrition and Toxicology, Karolinska University Hospital, Huddinge, S-141 86 Stockholm, Sweden.
Gastroenterology
|April 9, 2008
Summary
Hypophysectomy doubles intestinal cholesterol absorption, leading to hypercholesterolemia. Thyroid hormone is key in regulating this absorption and hepatic cholesterol secretion, impacting overall cholesterol metabolism.
Area of Science:
- Endocrinology
- Metabolic Research
- Cholesterol Metabolism
Background:
- Hypopituitarism is linked to dyslipidemia.
- Cholesterol metabolism is significantly altered in hypopituitary states.
Purpose of the Study:
- To investigate the impact of hypophysectomy on cholesterol and bile acid metabolism.
- To elucidate the role of pituitary hormones in regulating cholesterol absorption and transport.
Main Methods:
- Studied intact and hypophysectomized rats.
- Administered dietary cholesterol, ezetimibe, and hormonal substitutions (growth hormone, cortisone, thyroid hormone).
Main Results:
- Hypophysectomized rats showed doubled intestinal cholesterol absorption, which ezetimibe did not fully correct.
- Thyroid hormone normalized cholesterol absorption and stimulated hepatic ABCG5/G8 expression.
- Hepatic expression of cholesterol transporters (ABCG5/G8) and Cyp7a1 was reduced but normalized by cholesterol feeding.
Conclusions:
- Pituitary control, primarily via thyroid hormone, significantly influences intestinal cholesterol absorption.
- Thyroid hormone strongly stimulates hepatic cholesterol secretion and ABCG5/G8 expression in hypophysectomized rats.
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