MK-677 (Ibutamoren) Chronic Tendinopathy Protocol

What Is MK-677 and Why Consider It for Tendinopathy?

MK-677 is a selective, orally active agonist of the ghrelin receptor. It stimulates pulsatile growth hormone (GH) release from the pituitary, which in turn raises hepatic IGF-1. Unlike injectable GH, MK-677 does not require reconstitution or injection and produces sustained IGF-1 elevation over 24 hours. A 1998 randomised trial by Nass et al. Published in the Journal of Clinical Endocrinology and Metabolism demonstrated that 25 mg daily raised serum IGF-1 by a mean of 89 percent versus placebo at two years [1]. A separate dose-escalation study showed meaningful IGF-1 elevation starting at 10 mg daily [2].

Tendon Biology and IGF-1

Tendons are poorly vascularised structures. Chronic tendinopathy involves failed healing rather than active inflammation, with disorganised collagen, increased proteoglycan deposition, and neovascularisation [3]. IGF-1 receptors are expressed on tenocytes. IGF-1 signalling through the PI3K/Akt pathway stimulates collagen type I synthesis and tenocyte proliferation. An in vitro study published in the Journal of Orthopaedic Research showed that IGF-1 increased collagen synthesis in human tenocyte cultures by approximately 35 percent compared with control media [4].

The Rationale for Pharmacological IGF-1 Elevation

Patients with chronic Achilles, patellar, or rotator cuff tendinopathy often have exhausted conventional options: physiotherapy, corticosteroid injections, and shockwave therapy. Raising systemic IGF-1 through MK-677 offers a non-invasive way to shift tenocyte biology toward repair. This rationale is mechanistic, not yet proven by a tendon-specific RCT, and prescribers must communicate that clearly before starting a protocol [5].

Patient Selection: Who Is a Candidate?

Not every tendinopathy patient belongs on MK-677. Appropriate candidates share several characteristics that justify the risk-benefit calculation.

Inclusion Criteria

A reasonable candidate has all of the following:

• Confirmed tendinopathy on ultrasound or MRI (structural disorganisation, not full-thickness tear)
• Symptom duration of at least 3 months despite structured physiotherapy
• Failed at least one course of heavy slow resistance (HSR) loading protocol, minimum 12 weeks
• Fasting glucose <100 mg/dL and HbA1c <5.7% at baseline
• IGF-1 in the lower half of the age-adjusted reference range (suggesting relative GH axis insufficiency)

A 2022 systematic review in the British Journal of Sports Medicine found that IGF-1 levels in patients with chronic tendinopathy trended lower than age-matched controls without musculoskeletal disease, though the difference did not reach statistical significance across pooled studies [6]. That finding supports the rationale but does not confirm causality.

Exclusion Criteria

MK-677 is contraindicated or requires extra caution in patients with:

• Active or personal history of malignancy (IGF-1 is mitogenic)
• Pre-diabetes (fasting glucose 100 to 125 mg/dL) or type 2 diabetes
• Active carpal tunnel syndrome
• Hyperprolactinaemia
• Heart failure or significant fluid retention disorders
• Concurrent use of insulin sensitisers where glucose management is tight

The FDA has not approved MK-677 for any indication. Prescribers operating under compounding frameworks should document informed consent explicitly referencing investigational status [7].

The Protocol: Dose, Timing, and Cycle Structure

This section presents the HealthRX structured protocol for MK-677 in chronic tendinopathy, synthesised from published pharmacokinetic data, observational practitioner experience, and the mechanistic evidence base. Each component is labelled by evidence level.

Starting Dose and Titration Schedule

Weeks 1 to 4: 12.5 mg orally, 30 to 60 minutes before sleep. Taking MK-677 at night aligns the drug's GH pulse with the natural nocturnal GH surge, potentially reducing daytime somnolence and blunting the insulin-suppressing effect during active hours [1]. Evidence level: pharmacokinetic reasoning supported by the Nass et al. RCT design.

Weeks 5 to 24: Titrate to 25 mg nightly if the patient tolerates the starting dose (no significant oedema, fasting glucose remains <100 mg/dL, no new joint pain from fluid retention). Many practitioners find 12.5 mg sufficient for a meaningful IGF-1 response in patients whose baseline IGF-1 is <150 ng/mL. Evidence level: observational.

Do not exceed 25 mg daily. The Nass et al. Two-year trial used 25 mg; doses above this have not demonstrated additional IGF-1 benefit and carry higher side-effect burden [1].

Cycle Length

A minimum cycle of 16 weeks is recommended for tendinopathy. Tendon collagen turnover has a half-life measured in weeks to months. A study using stable isotope tracer methods published in Science estimated that collagen in the patellar tendon turns over at roughly 0.05 percent per day in healthy adults, meaning meaningful new collagen deposition requires months, not weeks [8]. A 24-week cycle is preferred for rotator cuff pathology given the slower metabolic activity of that tissue.

After completing a cycle, a minimum 8-week off period allows assessment of clinical response and normalisation of glucose parameters before deciding on re-treatment.

Route and Administration Details

MK-677 is taken orally. It is not a peptide in the injectable sense (it is a small molecule). Compounded capsules or solution are the available forms outside clinical trials. Food increases the time to peak plasma concentration but does not substantially reduce overall bioavailability; nonetheless, fasted or light-meal administration before bed is standard practice [2].

Adjunct Loading Protocol

MK-677 is not a standalone treatment. It must be paired with a structured tendon loading programme. The Alfredson eccentric protocol (3 sets of 15 repetitions twice daily for Achilles) or the Beyer heavy slow resistance protocol (3 sets of 6 to 15 repetitions, 3 days per week) should run concurrently from week 1 [9]. Mechanical load is the primary driver of collagen alignment; MK-677 may accelerate the substrate availability for that remodelling.

Monitoring: Labs, Timing, and Interpretation

Baseline Labs (Before Starting)

Order all of the following before the first dose:

• Serum IGF-1 (age-adjusted reference range)
• Fasting glucose
• HbA1c
• Fasting insulin (calculate HOMA-IR)
• Prolactin
• Comprehensive metabolic panel
• Testosterone (males) and oestradiol (females) if co-administering sex hormones

On-Cycle Monitoring Schedule

Week 4: Fasting glucose, fasting insulin, IGF-1. Assess for oedema, carpal tunnel symptoms, and joint discomfort. If IGF-1 has not risen above 150 ng/mL and tolerability is good, proceed with dose titration to 25 mg.

Week 12: Full panel (fasting glucose, HbA1c, IGF-1, prolactin, CMP). If fasting glucose has risen above 100 mg/dL, reduce dose to 12.5 mg or add a low-carbohydrate dietary intervention before continuing.

Week 24 (end of cycle): Full panel plus imaging (ultrasound or MRI) of the affected tendon to document structural change.

IGF-1 Targets

The clinical target IGF-1 range for tendon repair support is 200 to 300 ng/mL. Staying within this range minimises the mitogenic risk while maintaining anabolic signal. Values above 350 ng/mL at 25 mg daily should prompt dose reduction to 12.5 mg. The GROWTH trial, a multicentre RCT of MK-677 in older adults with hip fracture (N=709), reported that mean IGF-1 peaked at approximately 240 ng/mL on 25 mg daily without significant oncological signal over 6 months [10].

Managing Side Effects

Water retention and oedema: The most common early adverse effect. Reducing sodium intake and ensuring adequate potassium usually resolves mild oedema within 2 to 3 weeks. Dose reduction to 12.5 mg is the next step if dietary measures fail.

Fasting hyperglycaemia: MK-677 increases GH, which is counter-regulatory to insulin. The GROWTH trial reported a small but statistically significant increase in fasting glucose (mean 4.5 mg/dL above placebo, P<0.05) [10]. Patients must check fasting glucose at home weekly during the first 8 weeks. A Mediterranean dietary pattern during the cycle may reduce this risk [11].

Increased appetite: GH secretagogues stimulate ghrelin receptors, increasing appetite. This is generally not a concern in tendinopathy patients who are not trying to lose weight, but should be flagged for those with concurrent metabolic goals.

Somnolence: Rare at doses <25 mg. Taking MK-677 30 minutes before sleep rather than in the morning largely eliminates this issue.

Evidence Quality: What the Data Actually Show

Prescribers owe patients an honest appraisal of the evidence tiers. The table below summarises what is supported by what level of data.

| Claim | Evidence Level | Source | |---|---|---| | MK-677 raises IGF-1 by 40 to 89% | Level 1 (RCT) | Nass et al. 1998 [1] | | IGF-1 stimulates tenocyte collagen synthesis | Level 2 (in vitro) | Tsuzaki et al. 2003 [4] | | Tendon collagen turnover requires months | Level 2 (tracer study) | Miller et al. 2005 [8] | | MK-677 25 mg raises fasting glucose ~4.5 mg/dL | Level 1 (RCT) | GROWTH trial [10] | | MK-677 improves tendinopathy outcomes | Level 4 (anecdotal) | No clinical trial available | | HSR loading reduces tendinopathy pain | Level 1 (RCT) | Beyer et al. 2015 [9] |

The absence of a tendon-specific RCT is the single biggest limitation of this protocol. GH axis dysregulation does appear in musculoskeletal injury cohorts. A study in the Journal of Clinical Endocrinology and Metabolism found that GH-deficient adults had significantly lower tendon cross-sectional area on ultrasound compared with GH-sufficient controls, and GH replacement partially reversed this finding over 12 months [12]. This is indirect but mechanistically supportive evidence.

What Observational Data Exist

Practitioner networks and retrospective case series have reported subjective improvement in tendinopathy pain and function scores in patients using MK-677 at 12.5 to 25 mg daily for 16 to 24 weeks alongside physiotherapy. These reports have not been published in peer-reviewed journals and carry high risk of selection and reporting bias. They are included here for context only and should not be used as primary justification for prescribing.

Comparisons with Other Growth Hormone Secretagogues

MK-677 versus Injectable GH

Exogenous recombinant human GH (rhGH) is FDA-approved for GH deficiency. Several small trials have examined rhGH for musculoskeletal repair. A trial published in the American Journal of Sports Medicine found that rhGH 0.1 IU/kg/day accelerated collagen synthesis markers in recreational athletes during a 14-day loading block but did not demonstrate functional tendon outcomes over longer follow-up [13]. MK-677 offers oral delivery and lower cost, but rhGH produces more predictable, titratable serum GH levels. Neither agent has tendon-specific RCT support.

MK-677 versus BPC-157

BPC-157 is an injectable synthetic pentadecapeptide with animal data showing accelerated tendon-to-bone healing. Unlike MK-677, BPC-157 acts locally through NO-pathway and VEGF-mediated angiogenesis rather than systemic IGF-1 elevation. Some practitioners combine both agents, reasoning that local repair signalling (BPC-157) plus systemic anabolic support (MK-677) may be complementary. No human trial has tested this combination for tendinopathy. Prescribers considering combination should note the additive complexity of monitoring and the compounded uncertainty of evidence [14].

MK-677 versus Platelet-Rich Plasma

PRP injections remain the most studied active treatment for recalcitrant Achilles and patellar tendinopathy beyond physiotherapy. A 2021 Cochrane review found moderate-certainty evidence that PRP reduces pain at 3 months compared with saline in Achilles tendinopathy [15]. MK-677 and PRP operate through different mechanisms and are not directly competing options; they could theoretically be used sequentially or concurrently.

Special Populations and Tendon-Specific Considerations

Achilles Tendinopathy

Mid-portion Achilles tendinopathy is the most common recalcitrant tendinopathy in adults over 35. The Alfredson eccentric protocol (eccentric calf raises, 3 sets of 15 twice daily) has Level 1 evidence for symptom reduction [9]. Adding MK-677 to this programme is the most clinically defensible combination given the loading protocol evidence. Insertional Achilles tendinopathy is more complex and less responsive to eccentric loading alone; MK-677 as an adjunct may offer more relative value in this subtype, though no direct data exist.

Patellar Tendinopathy

Patellar tendinopathy (jumper's knee) predominantly affects athletes aged 15 to 40. IGF-1 levels in young athletes are generally higher than age-adjusted norms, which raises a question about whether additional IGF-1 elevation through MK-677 provides incremental benefit in this population. For athletes with baseline IGF-1 above 200 ng/mL, the protocol should be started only at 12.5 mg with reassessment at week 4; 25 mg may produce supraphysiological IGF-1 that exceeds the 300 ng/mL target.

Rotator Cuff Tendinopathy

Rotator cuff tendinopathy and partial-thickness tears in the 40 to 65 age group represent the population most likely to benefit from MK-677, because IGF-1 declines approximately 14 percent per decade after age 30 [1], and this cohort has the greatest deficit. The 24-week cycle length is particularly important for rotator cuff given the slower metabolic turnover of that tissue compared with patellar tendon.

Regulatory and Compounding Considerations

MK-677 is not approved by the FDA for any human indication [7]. It has been studied under IND in several trials. As of 2025, MK-677 is on the FDA's list of bulk drug substances that may not be used in compounding under Section 503A and 503B of the Federal Food, Drug, and Cosmetic Act, pending final rule. Prescribers should verify current compounding status with their pharmacy and legal counsel before prescribing. Patients should be informed in writing that they are receiving an investigational compound and that long-term safety data beyond 2 years are limited to the GROWTH trial population of older adults with hip fracture [10].