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Thyroid hormone is essential for pituitary somatotropes and lactotropes
J H Stahl1, S K Kendall, M L Brinkmeier
1Department of Human Genetics, University of Michigan Medical School, Ann Arbor 48109-0638, USA.
Endocrinology
|March 31, 1999
Summary
Thyroid hormone is crucial for maintaining proper anterior pituitary cell proportions. T4 replacement therapy in alphaGsu mutant mice normalized lactotropes and allowed gonadotrope hypertrophy, highlighting thyroid hormone
Area of Science:
- Endocrinology
- Molecular Biology
- Reproductive Biology
Background:
- The alpha-subunit is essential for thyroid-stimulating hormone (TSH), luteinizing hormone (LH), and follicle-stimulating hormone (FSH) activity.
- Mice lacking the alpha-subunit (alphaGsu-/-) display hypothyroidism and hypogonadism, mirroring TSH receptor-deficient (hyt) and GnRH-deficient (hpg) models.
- Anterior pituitary cell proportions are significantly altered in alphaGsu-/- mice despite the presence of all five major hormone-producing cell types.
Purpose of the Study:
- To investigate the role of the alpha-subunit and thyroid hormone in regulating anterior pituitary cell populations.
- To compare the pituitary phenotypes of alphaGsu-/- mice with existing hypothyroid and hypogonadal models.
- To elucidate the specific contributions of thyroid hormone (T4) versus the alpha-subunit to lactotrope and gonadotrope function and proliferation.
Main Methods:
- Phenotypic analysis of alphaGsu-/- mice.
- Histological examination of anterior pituitary cell types and proportions.
- Thyroxine (T4) replacement therapy in alphaGsu-/- mice to assess functional recovery.
Main Results:
- AlphaGsu-/- mice exhibit altered anterior pituitary cell proportions, with thyrotropes hypertrophied and hyperplasia, and somatotropes and lactotropes underrepresented.
- Lactotrope reduction is more severe in alphaGsu-/- mice compared to hyt and hpg mutants.
- T4 replacement normalized lactotropes and permitted gonadotrope hypertrophy in alphaGsu-/- mice, indicating T4's critical role in their proliferation and function.
Conclusions:
- Thyroid hormone, not the alpha-subunit itself, is vital for establishing correct anterior pituitary cell proportions.
- T4 is essential for lactotrope proliferation and function, and permissive for gonadotrope hypertrophy.
- This study underscores the significant impact of thyroid hormone on the developmental regulation of anterior pituitary cell populations.