Tesamorelin vs MK-677

An approved injection against an unapproved capsule

Both raise growth hormone and IGF-1, and the gap between them is regulatory as much as pharmacological. Tesamorelin is FDA-approved, injected, and has a specific documented effect: 15–18% reduction in visceral fat in HIV lipodystrophy trials. MK-677 is an oral capsule that produced genuinely good trial data, with IGF-1 restored to young-adult levels over two years, and was never approved anyway; development simply stopped. Notably MK-677 did not reduce fat, unlike the injected secretagogues, and it worsens insulin sensitivity.

An anterior pituitary tissue fragment with small capillaries and hormone secretory cells, three-dimensional histology-inspired view.

Tesamorelin Growth hormone Egrifta Full entry →

Human pituitary and nearby hypothalamic region viewed from below in a partial brain cutaway.

MK-677 Growth hormone Ibutamoren, Ibutamoren mesylate, L-163,191 Full entry →

Tesamorelin compared with MK-677
	Tesamorelin	MK-677
Evidence behind it	Human trials	Human trials
Worth knowing	Visceral fat returns when it is stopped. It can worsen glucose tolerance.	Despite good trial data it was never approved — development stopped. It raises blood glucose and reduces insulin sensitivity, and the fat-free mass it adds includes water. Sustained IGF-1 elevation carries the same theoretical cancer concern as other growth signalling.
Approval	Approved · US	In trials
Category	Growth hormone	Growth hormone
What it is	The full 44-amino-acid growth-hormone-releasing hormone with a small fatty group added at one end to slow its breakdown. It raises the body's own growth hormone and IGF-1 and reduces deep abdominal fat. It is also studied for fatty liver and mild cognitive impairment.	Not a peptide, but it acts on the same receptor as the peptide growth hormone secretagogues. It is an orally active ghrelin receptor agonist, which is unusual: most of this class must be injected. A single daily capsule raises growth hormone and IGF-1 for about 24 hours.
How it works	A GHRH analogue that stimulates natural pulsatile growth hormone release; its signature effect is on visceral fat.	Agonist at the ghrelin receptor (GHS-R1a) — the same target as GHRP-2, GHRP-6 and ipamorelin — but orally bioavailable and long-acting.
What studies report	Roughly 15-18% reduction in visceral abdominal fat in HIV lipodystrophy trials Reduced liver fat in people with HIV and fatty liver Modest cognitive signals in mild cognitive impairment studies	Raised IGF-1 in older adults to levels typical of young adults in a 2-year trial Increased fat-free mass by about 1.1 kg versus placebo in that trial Did not reduce fat mass, unlike injected secretagogues Trialled for hip-fracture recovery and muscle wasting
Dosing	From studies 2 mg daily, subcutaneous — Phase 3, HIV-associated lipodystrophy (n≈800). 15–18% reduction in visceral fat 2 mg daily, subcutaneous — NIH trial in HIV with fatty liver. Reduced liver fat Reported, not evidence 1–2 mg daily, often taken before bed Run for 3+ months, since visceral fat returns on stopping	From studies 25 mg daily, oral — Trial in healthy older adults. IGF-1 restored to young-adult levels; +1.1 kg fat-free mass; no fat loss 25 mg daily, oral — Hip fracture recovery trial. Improved gait speed in some measures Reported, not evidence 12.5–25 mg once daily, on an empty stomach Often cycled over concerns about sustained IGF-1 elevation
Why people take it	Visceral belly fatLiver fatLean muscle preservationGrowth hormone support	Growth hormone and IGF-1 elevationLean mass and bone densitySleep qualityAppetite stimulation
In practice	Used specifically for visceral fat rather than general weight loss Run for longer periods than most peptides, since the fat returns when stopped Sold pre-blended with ipamorelin in a single vial, pairing a growth hormone releasing factor with a secretagogue	Popular precisely because it is oral and once daily Water retention and increased appetite are commonly reported Often run in cycles rather than continuously, over concerns about sustained IGF-1 elevation
Route	Subcutaneous injection, prescribed where approved	Oral capsule — a small molecule, so digestion is not a barrier

Rows describing reported use say what people do, not what has been shown to work. Evidence strength is graded the same way across the whole library, so the two columns are directly comparable.

Read the full entries

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Educational information only. Nothing here is medical advice, a dosing protocol, or a recommendation to use any compound. Comparing two compounds is not a suggestion to take either one. Talk to a licensed clinician before acting on anything you read here. How to read these entries.