Hormonal & Reproductive WellnessPerformance

FST

Follistatin

Also known as: FS

Myostatin antagonist that promotes muscle growth and metabolic health.

Biological Function

Follistatin is a glycoprotein that binds and neutralizes myostatin (MSTN) and activins, removing the primary brake on skeletal muscle growth. By inhibiting myostatin signaling, follistatin promotes muscle hypertrophy, enhances fat oxidation, and improves insulin sensitivity. The FST/MSTN axis is a central regulator of body composition.

Why Biomeme Monitors This Target

The follistatin-myostatin ratio is a key transcriptomic readout for anabolic therapies. TRT upregulates follistatin and suppresses myostatin via AR-mediated signaling. Monitoring FST expression provides molecular evidence of whether testosterone or growth hormone therapies are shifting the muscle growth axis in the intended direction.

Expression Context

Upregulated by testosterone, exercise (especially resistance training), and growth hormone. Expression varies significantly by tissue (highest in reproductive tissues and liver). Serum follistatin rises acutely after exercise.

Signaling Pathway

AR/GH Signaling FST Transcription Myostatin Binding/Neutralization Muscle Growth

Associated Therapies

Testosterone / TRT

TRT upregulates follistatin expression via androgen receptor signaling

Ipamorelin

GH secretagogues may modulate the FST/MSTN axis through IGF-1 signaling

Quick Facts

Symbol: FST
Category: Hormonal & Reproductive
Applications: Wellness, Performance
Linked Therapies: 2

References

[1] Follistatin-Myostatin Axis — FASEB J 2014

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