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ForumsTirzepatide (Mounjaro / Zepbound)GIP receptor: the underappreciated half of tirzepatide's mechanism — need advice Page 2

GIP receptor: the underappreciated half of tirzepatide's mechanism — need advice

Dr.EM_Chicago Tue, Nov 4, 2025 at 7:40 AM 15 replies 1,283 viewsPage 2 of 3
BethLabQueen
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Nov 4, 2025 at 9:26 AM#6

The figures, for anyone assembling their own picture. Numbers worth memorising for this class: Tmax one to three days for the weekly peptides, terminal half-life about a week for semaglutide and about five days for tirzepatide, steady state at four to five half-lives, subcutaneous bioavailability high enough that site choice is irrelevant.

8 11maya_sedona, stefan_berlin, Dr.EM_Chicago and 5 others
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sarah_TO
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Nov 4, 2025 at 10:07 AM#7

A narrower follow-up, since the general answer is now clear:

How much of the tirzepatide advantage is the GIP component and how much is simply that the dose ladder goes higher in receptor-occupancy terms?

9 12Dr.EndoEP, GraceAZ_72, carl_compliance and 6 others
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james_edin
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Nov 4, 2025 at 10:48 AM#8
BethLabQueen said:
Numbers worth memorising for this class: Tmax one to three days for the weekly peptides, terminal half-life about a week for semaglutide and about…

Adding the part of the answer the thread has not reached. The mechanism is more central than most summaries suggest. Receptor agonism in the arcuate nucleus activates POMC neurons and inhibits AgRP/NPY signalling, and the downstream MC4R pathway is the same one disrupted in monogenic obesity — convergent genetic evidence that the target is the right one. Peripherally there is glucose-dependent insulin secretion, glucagon suppression and delayed gastric emptying, but the gastric component largely adapts over months while the central effect persists, which is why the durable effect is appetite rather than fullness.

Worth separating that from the pharmacology, which this thread keeps folding into the same question. They behave differently and the advice does not transfer.

10 13tane_welly, Dr.PathRoch, mona_PHX and 7 others
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Dr.EM_Chicago
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Nov 4, 2025 at 11:29 AM#9

Reporting back.

Update: the eight-week restart pattern people described is exactly what happened. I nearly abandoned it at week five.

Last edited: Nov 4, 2025 at 3:29 PM
11 14lucas_SP_BR, lisa_labSD, adam_van and 8 others
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hans_munich
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Nov 4, 2025 at 2:45 PM#10
james_edin said:
The mechanism is more central than most summaries suggest.

True, though the ladder is longer and that is not a neutral detail — six dose steps means six opportunities to stall on the way up, and plenty of people never reach the dose the headline number came from.

Correct me if the detail matters more than I have assumed.

Last edited: Nov 4, 2025 at 8:45 PM
21 21emma_london, tammy_FL, Dr.LipidDallas and 18 others
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