Hypothalamic obesity after hypophysectomy or adrenalectomy: dependence on corticosterone

Area of Science:

• Neuroendocrinology
• Physiology
• Obesity Research

Background:

• Ventromedial hypothalamus (VMH) lesions cause hyperphagia and obesity.
• Complete adrenalectomy prevents VMH-induced obesity, but effects of hypophysectomy are less clear.
• Adrenal glucocorticoids are implicated in the VMH obesity syndrome.

Purpose of the Study:

• To directly compare the effects of hypophysectomy and adrenalectomy on VMH-induced obesity in rats.
• To elucidate the role of adrenal glucocorticoid hormones in the manifestation of hypothalamic obesity.

Main Methods:

• Adult female rats underwent VMH lesions or sham lesions.
• Rats were subjected to complete adrenalectomy or hypophysectomy.
• Plasma corticosterone and ACTH levels were measured.
• Intracranial self-stimulation was assessed.

Main Results:

• Complete adrenalectomy completely suppressed VMH-induced weight gain but did not affect intracranial self-stimulation.
• Hypophysectomy suppressed weight gain, but HYPOX-VMH rats gained more weight than controls.
• Low levels of corticosterone and ACTH in HYPOX-VMH rats correlated with significant weight gain.
• Incompletely adrenalectomized rats with low corticosterone levels also showed VMH-induced weight gain.

Conclusions:

• Adrenal glucocorticoid hormones play a permissive role in the VMH obesity syndrome.
• Only minimal levels of adrenal glucocorticoids are required for the development of hypothalamic obesity.
• The pituitary's role in VMH obesity is likely mediated through adrenal glucocorticoid secretion.