Doctoral defence: Keiu Heinla „Effects of GLP-1 receptor agonists on pituitary and adrenal hormones”

On December 11th Keiu Heinla will defend her thesis „Effects of GLP-1 receptor agonists on pituitary and adrenal hormones”.

Supervisor:
Professor Vallo Volke, University of Tartu

Opponent:
Professor Valdis Pirags, University of Latvia (Latvia)

Summary:
Glucagon-like peptide 1 (GLP-1) is an incretin hormone. The most important stimulus for its secretion is the digestion process of nutrients, especially carbohydrates. GLP-1 stimulates insulin release in a glucose-dependent manner, thus playing an important role in postprandial insulin release.

GLP-1 receptor agonists are a relatively new group of drugs for type 2 diabetes that, in addition to controlling blood glucose, have a significant number of effects on other organ systems. In recent years, the weight-loss effects of GLP-1 receptor agonists have received a lot of attention, leading to high demand for the drug and supply difficulties.

The aim of this project was to investigate whether acute or chronic administration of GLP-1 receptor agonists affects the blood levels of various pituitary and adrenal hormones (renin, aldosterone, growth hormone) in humans.

As part of the doctoral thesis, two clinical trials were conducted on healthy volunteers. These were open-label pilot studies without placebo group. Subjects received liraglutide subcutaneously for 21 days (clinical trial 1) or a single dose of exenatide (clinical trial 2).

It was concluded that GLP-1 receptor agonist administration led to suppression of the renin-angiotensin-aldosterone system (RAAS) in healthy adults. These findings may help explain the reno- and cardioprotective effects of GLP-1 receptor agonists. In addition, a single dose of a GLP-1 receptor agonist resulted in moderate central stimulation of the hypothalamic-pituitary-adrenal (HPA) axis, so GLP-1 receptor administration may be clinically useful for testing pituitary insufficiency. It was also shown that a single dose of a GLP-1 receptor agonist induced a sharp increase in growth hormone levels via central mechanism of action.