Pituitary gland function after disconnection from direct hypothalamic influences in the sheep

Area of Science:

• Endocrinology
• Neuroscience
• Surgical Innovation

Background:

• The pituitary gland's function is tightly regulated by hypothalamic control.
• Previous surgical methods for isolating the pituitary often resulted in gland infarction.
• A reliable method for creating an isolated pituitary in vivo was needed.

Purpose of the Study:

• To describe a novel surgical procedure for achieving hypothalamo-pituitary disconnection (HPD) in sheep.
• To evaluate the effectiveness of HPD in functionally isolating the pituitary gland while maintaining its vascular supply.
• To establish an in vivo model for studying the isolated pituitary gland.

Main Methods:

• A transnasal, transsphenoidal approach was used to access the median eminence, pituitary stalk, and anterior pituitary.
• Hypothalamo-pituitary disconnection (HPD) was achieved by entering the median eminence above the portal circulation and removing nervous tissue.
• Surgical outcomes, pituitary gland vascularization, and hormonal levels (LH, FSH, prolactin) were assessed.

Main Results:

• HPD effectively disconnected the pituitary from hypothalamic control with minimal pars distalis infarction (1/10 cases).
• The procedure maintained blood supply to the pituitary gland.
• Plasma LH and FSH decreased, while prolactin increased post-HPD.
• Isolated pituitaries responded to gonadotropin-releasing hormone (GnRH) with LH release, confirming functional isolation.

Conclusions:

• Hypothalamo-pituitary disconnection (HPD) is an effective surgical technique for creating an isolated pituitary gland model in sheep.
• This model allows for the study of pituitary function independent of direct hypothalamic influence.
• HPD preserves pituitary viability and responsiveness to specific stimuli, offering a valuable research tool.