Side-by-side · Research reference

Follistatin-344vsHGH 191AA

Side-by-side comparison across mechanism, dosage, evidence, side effects, administration, and stack synergies. Citations on every claim where available.

AHuman-MechanisticHUMAN-REVIEWED4/58 cited

BFDA-ApprovedHUMAN-REVIEWED0/75 cited

Follistatin-344

Myostatin/Activin Antagonist · Research Use

15–25%FST/MSTN ratio ↑

344 AACirculating isoform

ResearchPhase status

Research · No approved protocol

HGH 191AA

Recombinant hGH · FDA-Approved

0.024–0.034 mg/kg/dayPediatric GHD dose

2–4 hoursPlasma half-life

191 AASequence length

SQ · Daily · Evening preferred

01Mechanism of Action

Parameter

Follistatin-344

HGH 191AA

Primary target

Myostatin (MSTN/GDF-8) and Activin A

Growth hormone receptor (GHR) — JAK2/STAT5 pathway

Pathway

FST-344 binds MSTN/Activin → prevents ActRIIB receptor engagement → disinhibits muscle anabolism

GHR activation → JAK2/STAT5 → liver IGF-1 synthesis + direct metabolic effects

Downstream effect

Elevated follistatin/myostatin ratio, increased muscle protein synthesis, attenuated muscle atrophy signalingJeong 2026

Linear growth, lipolysis, protein synthesis, nitrogen retention, carbohydrate metabolism modulation

Feedback intact?

Yes — indirect antagonist, preserves endogenous regulation

No — exogenous GH bypasses hypothalamic-pituitary axis, suppresses endogenous pulsatility

Origin

Endogenous glycoprotein, 344-AA isoform lacking heparin-binding domain (vs FST-315)

Recombinant DNA technology — 191 AA, identical to pituitary hGH, no methionyl residue

Antibody development

Not documented in available trials (endogenous protein)

Rare — <2% develop binding antibodies, typically non-neutralizing

02Dosage Protocols

Parameter

Follistatin-344

HGH 191AA

Clinical protocol

None — no approved dosing regimen

Follistatin-344 measured as endogenous biomarker, not administered exogenously in cited trials.

—

Research context

Endogenous modulation via exercise + nutrition

Resistance training + EAA intake elevated FST/MSTN ratio by 15–25% in 12-week RCT (older women).

—

Evidence basis

Human observational / biomarker studies

FDA-approved / decades of RCT data

Half-life

Not established

Circulating isoform; lacks tissue-binding domain of FST-315.

—

Pediatric GHD

—

0.024–0.034 mg/kg/day SQ

6–7× per week dosing typical. Brand-specific ranges.

Adult GHD

—

0.004–0.016 mg/kg/day SQ

Start low, titrate based on IGF-1 levels.

Turner syndrome

—

0.045–0.050 mg/kg/day SQ

Idiopathic short stature

—

0.037 mg/kg/day SQ

AIDS wasting

—

0.1 mg/kg/day SQ (high-dose)

Short-term indication. Monitor glucose.

Frequency

—

Once daily, typically evening

Evening administration mimics physiological GH pulse.

Monitoring

—

IGF-1, glucose, thyroid function, bone age (children)

Duration

—

Years (children until epiphyseal closure); indefinite (adult GHD)

03Metabolic / Fat Loss Evidence

Parameter

Follistatin-344

HGH 191AA

Primary target

Muscle mass preservation, not direct lipolysis

—

Indirect fat effect

Increased lean mass → elevated resting metabolic rate

Not primary mechanism. Muscle-sparing during deficit.

—

Clinical evidence

Lorcaserin trial (6 mo) showed no MAFI axis changes during fat lossRamirez-Cisneros 2026

Suggests follistatin not primary driver of fat loss in weight-reduction interventions.

—

GLP-1RA studies

Liraglutide (35 days) — no significant MAFI axis modulation despite fat/lean changes

—

Primary fat target

—

Visceral and subcutaneous adipose tissue

Mechanism

—

Lipolysis via hormone-sensitive lipase activation, FFA oxidation

Effect on lean mass

—

Significant lean mass increase (protein synthesis, nitrogen retention)

Insulin sensitivity

—

Acute insulin resistance (anti-insulin effect); chronic neutral-to-improved via fat loss

IGF-1 elevation

—

Dose-dependent, significant — primary anabolic mediator

Glucose metabolism

—

Hyperglycemia risk, especially high doses (AIDS wasting)

Body composition

—

↓ fat mass, ↑ lean mass, ↑ bone mineral density (children)

Clinical context

—

FDA-approved for AIDS wasting (cachexia). Off-label use for body recomposition lacks long-term safety data.

04Side Effects & Safety

Parameter

Follistatin-344

HGH 191AA

Clinical safety data

None — no human exogenous administration trials in literature

—

Theoretical risks

Excessive myostatin inhibition → muscle overgrowth, impaired glucose tolerance

Based on myostatin-null animal models and clinical myostatin inhibitor trials.

—

Endogenous elevation (exercise)

No adverse effects reported in 12-week resistance + EAA trials

—

Cancer risk (theoretical)

Myostatin inhibition may promote tumor growth in malignancy (preclinical data)

—

Regulatory status

Not approved for human use — research peptide only

—

Injection site reaction

—

Lipohypertrophy, lipoatrophy, erythema (rotate sites)

Fluid retention / Edema

—

Peripheral edema, arthralgia, carpal tunnel syndrome (dose-dependent)

Glucose intolerance

—

Hyperglycemia, new-onset diabetes (anti-insulin effect)

Intracranial hypertension

—

Benign intracranial hypertension (pseudotumor cerebri) — headache, visual changes, papilledema

Slipped capital femoral epiphysis

—

SCFE risk in children — limp, hip/knee pain (requires surgery)

Scoliosis progression

—

Rapid growth may unmask/progress scoliosis (monitor spine in children)

Hypothyroidism

—

Central hypothyroidism unmasking or worsening (monitor TSH, free T4)

Cancer risk

—

Contraindicated in active malignancy. Theoretical risk in cancer survivors (controversial).

Antibody formation

—

Rare (<2%), typically non-neutralizing. Loss of efficacy if neutralizing antibodies develop.

Pancreatitis

—

Rare. Higher risk in children with certain syndromes (Prader-Willi).

Gynecomastia

—

Adolescent males (physiological during puberty, may be exacerbated)

Absolute Contraindications

Follistatin-344

·Active malignancy
·No approved protocol — research use only

HGH 191AA

·Active malignancy or history of cancer (especially childhood cancer survivors with risk factors)
·Acute critical illness (post-cardiac surgery, trauma, acute respiratory failure)
·Diabetic retinopathy (active proliferative or severe non-proliferative)
·Prader-Willi syndrome with severe obesity, sleep apnea, or respiratory impairment
·Closed epiphyses (for growth indications)

Relative Contraindications

Follistatin-344

·Insulin resistance / Type 2 diabetes (monitor glucose)
·Pregnancy / lactation (unknown safety profile)

HGH 191AA

·Diabetes mellitus (monitor closely, may require insulin adjustment)
·Intracranial lesions or history of intracranial hypertension
·Scoliosis (monitor curve progression)
·Untreated hypothyroidism (treat before GH initiation)
·Severe obesity (assess OSA risk, cardiovascular status)

05Administration Protocol

Parameter

Follistatin-344

HGH 191AA

1. Regulatory status

Follistatin-344 is not approved for human administration. All cited studies measure endogenous serum follistatin as a biomarker, not as an exogenous therapeutic agent.

Add diluent (sterile water or bacteriostatic water per manufacturer) to vial. Swirl gently — do not shake. Solution should be clear, colorless. Concentration varies by brand (e.g., 5 mg or 10 mg per vial).

2. Endogenous modulation

Resistance exercise combined with essential amino acid (EAA) supplementation elevated the follistatin/myostatin ratio by 15–25% in 12-week randomized trials. Protein intake (1.2–1.5 g/kg/day) synergizes with training to upregulate endogenous follistatin.

Subcutaneous — rotate sites: abdomen, thigh, buttocks, upper arm. Avoid same site within 1 cm for 2 weeks to prevent lipodystrophy.

3. Measurement context

Serum follistatin and follistatin/myostatin ratio are used diagnostically in sarcopenia screening and as biomarkers of muscle anabolic balance in clinical trials.

Once daily, evening preferred (6–8 PM or pre-sleep). Mimics physiological nocturnal GH secretion. Consistency is critical.

4. Research consideration

Gene therapy and recombinant follistatin delivery are under preclinical investigation for muscular dystrophy and sarcopenia. No human safety or efficacy data for exogenous FST-344 administration.

Unreconstituted: refrigerate 2–8 °C, protect from light. Reconstituted: refrigerate, use within 14–28 days (brand-specific). Do not freeze.

5. Needle

—

27–31G, 4–8 mm insulin syringe or pen device. Pinch skin, 45–90° angle depending on subcutaneous thickness.

6. Monitoring

—

Baseline and periodic: IGF-1 (target age/sex-adjusted midrange), fasting glucose, HbA1c, thyroid function (TSH, free T4), bone age (children), lipid panel. Fundoscopy if headache/visual symptoms.

06Stack Synergy

Follistatin-344

+ BPC-157

Multi-pathway

View BPC-157 →

Follistatin-344 (myostatin antagonist) and BPC-157 (tissue repair peptide) address complementary pathways in muscle recovery. FST-344 promotes muscle protein synthesis by disinhibiting myostatin signaling, while BPC-157 accelerates healing of tendons, ligaments, and microtears via angiogenesis and collagen synthesis. Combined, they may support both hypertrophy and structural repair during high-volume training or injury recovery.

Follistatin-344: No approved protocol — endogenous modulation via resistance exercise + EAA
BPC-157: 250–500 mcg SQ · twice daily · near injury site or systemic
Duration: 4–8 weeks
Primary benefit: Muscle hypertrophy + accelerated soft tissue repair

+ TB-500

Moderate

View TB-500 →

TB-500 (thymosin beta-4 fragment) promotes cell migration, angiogenesis, and anti-inflammatory signaling in muscle and connective tissue. Follistatin-344's anabolic signaling may synergize with TB-500's regenerative effects during muscle damage or overtraining, particularly in older adults where both myostatin inhibition and tissue repair are rate-limiting.

Follistatin-344: Endogenous upregulation (resistance training + protein)
TB-500: 2–5 mg SQ · twice weekly · loading phase 4 weeks, then maintenance
Frequency: Twice weekly TB-500, daily training stimulus for FST
Primary benefit: Enhanced recovery, reduced inflammation, muscle growth support

HGH 191AA

+ Ipamorelin

Moderate

View Ipamorelin →

Ipamorelin (GHRP) stimulates endogenous GH release, which is redundant when exogenous rhGH is administered. However, ipamorelin may still amplify pulsatility of remaining endogenous secretion in partial GHD or during GH dose titration. Not typically combined in standard clinical practice; more common in experimental or off-label protocols. Limited evidence for additive benefit.

HGH 191AA: Standard dose per indication
Ipamorelin: 100–200 mcg SQ · morning (if used)
Note: Monitor IGF-1 closely; avoid supraphysiological levels
Primary benefit: Theoretical enhancement of pulsatility; limited clinical rationale

+ Tesamorelin

Weak

View Tesamorelin →

Tesamorelin (GHRH analogue) stimulates endogenous GH secretion, which is unnecessary when exogenous rhGH is already provided. Combining both offers no mechanistic advantage and increases cost, side effects, and IGF-1 elevation risk. Not recommended in clinical practice.

Note: Combination not recommended — choose one GH modality
Primary benefit: None — redundant mechanisms