Development in calves and heifers after hypophysial stalk transection or hypophysectomy

Area of Science:

• Veterinary Endocrinology
• Reproductive Physiology
• Animal Growth and Development

Background:

• The pituitary gland plays a crucial role in regulating growth and sexual maturation.
• Disruptions to pituitary function can have profound effects on endocrine systems and development.

Purpose of the Study:

• To investigate the effects of hypophysial stalk transection and hypophysectomy on growth and sexual development in calves.
• To assess the impact of these procedures on gonadal function, accessory sex glands, and other endocrine organs.

Main Methods:

• Surgical transection of the hypophysial stalk or complete hypophysectomy was performed on prepuberal and mature calves.
• Sham-operated and unoperated calves served as controls.
• Hormonal responses and reproductive parameters were evaluated, including gonadotropin administration in mature heifers.

Main Results:

• Both hypophysial stalk transection and hypophysectomy markedly inhibited growth and arrested sexual development in young calves.
• Reproductive organs (testes, ovaries) showed significant regression, and secondary sexual characteristics were lost.
• Mature heifers, while experiencing follicular regression, showed restored ovarian function with exogenous gonadotropin administration.
• Thyroid and adrenal gland weights decreased and showed atrophy after hypophysectomy, but not after stalk transection.

Conclusions:

• Disruption of the hypophysial stalk or removal of the pituitary gland severely impairs growth and sexual maturation in young cattle.
• While these procedures cause significant endocrine and reproductive deficits, gonadal function in mature animals can be partially restored with exogenous gonadotropins.
• The differential effects on thyroid and adrenal glands suggest distinct roles for the stalk and pituitary in maintaining these organs.