Mounjaro

Tirzepatide is a dual GIPR/GLP-1R agonist. Both receptors couple to Gs signalling and cAMP pathways. Receptor assays show a pharmacological profile distinct from simply adding native GIP and GLP-1: activity is imbalanced, with biased signalling at GLP-1R and relatively reduced β-arrestin recruitment/internalisation in experimental systems.

These findings help explain the development rationale. They do not quantify how much each receptor contributes to an individual patient's weight loss.

Central appetite effects contribute to reduced energy intake. Glucose-dependent insulin secretion helps explain why hypoglycaemia is less likely in isolation than when treatment is combined with insulin or a sulfonylurea. Gastric emptying is delayed, but this effect diminishes with repeated dosing; it is not a complete explanation for sustained weight loss.

The fatty-acid modification promotes albumin binding and prolonged exposure, supporting weekly administration.

SURMOUNT-1 enrolled 2,539 adults with obesity, or overweight plus a weight-related complication, without diabetes. At 72 weeks, mean weight change with the treatment-regimen estimand was −15.0%, −19.5% and −20.9% at 5, 10 and 15 mg, versus −3.1% with placebo. This included a dose-escalation period and lifestyle support.

Results are not directly transferable to every population. SURMOUNT-4 tested continuation versus withdrawal after an open-label lead-in, selecting people able to progress through initial treatment. Neither study establishes a universal treatment duration.

Receptor and animal studies generate mechanistic hypotheses; clinical outcome trials test patient benefits. Avoid presenting GIP action as a proven, isolated fat-burning effect.

Australian monitoring advice includes mood symptoms and sudden visual loss. These precautions should not be described as proof of causation: TGA's vision review distinguished the stronger semaglutide signal from the evidence for tirzepatide. Recheck current Australian product information and safety updates before each publication.