Side-by-side · Research reference

Follistatin-344vsHCG

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-REVIEWED12/52 cited

Follistatin-344

Myostatin/Activin Antagonist · Research Use

15–25%FST/MSTN ratio ↑

344 AACirculating isoform

ResearchPhase status

Research · No approved protocol

HCG

Glycoprotein Hormone · LH Mimetic

2,000 IUTypical dose (2×/wk)Konsam 2026 Zachariou 2026

70–90%Sperm induction rateHuijben 2026 Zachariou 2026

12–24 moTime to sperm appearanceHuijben 2026 Nariyoshi 2025

IM or SQ · 2–3×/week

01Mechanism of Action

Parameter

Follistatin-344

HCG

Primary target

Myostatin (MSTN/GDF-8) and Activin A

LH receptors on testicular Leydig cellsSchröder-Lange 2025

Pathway

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

hCG → Leydig cell LH receptor → Intracellular cAMP → Steroidogenesis pathway activation → Testosterone synthesis

Downstream effect

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

Elevated intratesticular testosterone, restored spermatogenesis, virilization, secondary sex characteristic developmentKonsam 2026 Zachariou 2026

Feedback intact?

Yes — indirect antagonist, preserves endogenous regulation

No — exogenous hCG bypasses hypothalamic-pituitary axis; endogenous LH remains suppressed

Origin

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

Heterodimeric glycoprotein (alpha subunit shared with LH/FSH/TSH; beta subunit confers specificity). Available as urinary-derived or recombinant formulations.

Antibody development

Not documented in available trials (endogenous protein)

Rare with recombinant; possible with urinary-derived formulations

02Dosage Protocols

Parameter

Follistatin-344

HCG

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

RCT / Meta-analysis / FDA-approvedKonsam 2026 Huijben 2026

Half-life

Not established

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

—

Hypogonadotropic hypogonadism (monotherapy)

—

2,000 IU IM/SQ 2–3×/weekKonsam 2026 Zachariou 2026

Titrate to normalize testosterone (300–1,000 ng/dL) or achieve target AMH ~7.4 ng/mL.

Combined therapy (hCG + FSH)

—

hCG 2,000 IU 2×/wk + rFSH 75 IU 3×/wkKonsam 2026 Nariyoshi 2025

Preferred for azoospermia; FSH added after initial hCG phase or from outset.

Triple therapy (experimental)

—

hCG 2,000 IU 2×/wk + rFSH 75 IU 3×/wk + testosterone 100 mg IM q2wkKonsam 2026

May accelerate virilization; reduces hCG requirements (~30% lower cumulative dose vs monotherapy).

Cryptorchidism (pediatric)

—

500–4,000 IU IM 2–3×/week for 3–6 weeks

Duration to sperm appearance

—

12–24 months (median ~18 mo)Huijben 2026 Zachariou 2026

Congenital HH may require longer treatment; acquired HH responds faster.

Route

—

Intramuscular or subcutaneousKonsam 2026

Monitoring

—

Serum testosterone, semen analysis q3–6mo, testicular ultrasound

Thickened seminiferous tubules (>300 μm) on ultrasound predict imminent sperm appearance.Nariyoshi 2025

03Metabolic / Fat Loss Evidence

Parameter

Follistatin-344

HCG

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

—

04Side Effects & Safety

Parameter

Follistatin-344

HCG

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

—

Pain, erythema (mild, transient)

Gynecomastia

—

Aromatization of elevated testosterone to estradiol; dose-dependent

Testicular discomfort / Edema

—

Rapid testicular growth in hypogonadal males; usually self-limiting

Polycythemia

—

Elevated hematocrit from supraphysiological testosterone; monitor CBC

Mood / Libido changes

—

Variable; usually positive with normalization of testosterone

Acne / Oily skin

—

Androgen-mediated; dose-dependent

Prostate concerns

—

Monitor PSA in older males; hCG restores physiological testosterone (not supraphysiological)

Antibody formation

—

Rare with recombinant; possible with urinary-derived

Absolute Contraindications

Follistatin-344

·Active malignancy
·No approved protocol — research use only

HCG

·Androgen-dependent malignancy (prostate, breast cancer)
·Hypersensitivity to hCG or excipients
·Precocious puberty

Relative Contraindications

Follistatin-344

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

HCG

·Untreated obstructive sleep apnea
·Severe cardiovascular disease (polycythemia risk)
·History of thromboembolism

05Administration Protocol

Parameter

Follistatin-344

HCG

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 sterile water or bacteriostatic water per manufacturer instructions. Typically 1–2 mL per 5,000–10,000 IU vial. Roll gently — do not shake. Solution should be clear.

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.

Intramuscular: ventrogluteal, vastus lateralis, or deltoid. Subcutaneous: abdomen, avoiding navel (2-inch radius). Rotate sites to prevent lipohypertrophy.

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.

Administer 2–3 times per week. Consistent weekly schedule recommended (e.g., Monday/Thursday or Monday/Wednesday/Friday).

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.

Lyophilized: room temperature, light-protected. Reconstituted: refrigerate 2–8 °C. Bacteriostatic water extends shelf life to ~30 days; sterile water use within 72 hours.

5. Needle selection

—

IM: 21–23G, 1–1.5 inch. SQ: 25–27G, 5/8 inch. Inject slowly (30–60 seconds for IM).

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

HCG

— no documented stacks