Bromocriptine and glucose tolerance in acromegalics

Area of Science:

• Endocrinology
• Metabolic Disorders
• Pharmacology

Background:

• Acromegaly frequently presents with impaired glucose tolerance or diabetes mellitus.
• Elevated insulin levels and exaggerated insulin response during oral glucose tolerance tests (OGTT) are common in acromegaly.
• Growth hormone (GH) is a known contributor to glucose intolerance in acromegaly.

Purpose of the Study:

• To investigate the effects of bromocriptine on glucose metabolism and insulin secretion in patients with acromegaly.
• To determine if bromocriptine improves glucose tolerance independently of its effects on growth hormone levels.

Main Methods:

• A study involving 18 acromegaly patients treated with bromocriptine for up to 6 years.
• Repeated oral glucose tolerance tests (OGTT) and insulin tolerance tests (ITT) were performed.
• Measurements included blood glucose, immunoreactive insulin (IRI), and growth hormone (GH) levels.

Main Results:

• Bromocriptine improved glucose tolerance and normalized exaggerated insulin responses in non-diabetic acromegalics, even without significant GH reduction.
• In diabetic acromegalics, bromocriptine restored the ability to increase IRI during OGTT, improving glucose tolerance.
• Insulin tolerance tests showed higher IRI levels in patients on bromocriptine, suggesting enhanced insulin secretion or sensitivity.

Conclusions:

• Bromocriptine positively impacts glucose metabolism in acromegaly, suggesting mechanisms beyond GH reduction.
• The drug may protect pancreatic beta-cells from "exhaustion" and potentially reduce glucagon levels.
• Bromocriptine offers a therapeutic benefit for glucose intolerance associated with acromegaly.