Inositol – Cellular Signal Transduction, PCOS, and Mental Health

Inositol is a vitamin-like compound that the body can synthesize itself from glucose. As a component of cell membranes (phosphatidylinositol) and second messenger systems, it is involved in insulin signaling, serotonin transmission, and thyroid hormone synthesis. Its effect on PCOS (Polycystic Ovary Syndrome) is particularly well-documented.

Inositol Isomers: Myo- and D-Chiro-Inositol

Form	Occurrence	Main Function
Myo-Inositol (MI)	Most common in the body (~95% of inositol)	FSH signaling, insulin sensitivity in the ovary, serotonin
D-Chiro-Inositol (DCI)	~5% of inositol	Insulin second messenger in liver/muscle, androgen synthesis regulation in the ovary

The physiological MI:DCI ratio in the ovary is ~40:1. In PCOS, this ratio is disturbed (insulin resistance leads to increased DCI conversion) → too little MI in the ovary → disturbed FSH signaling → follicular maturation problems and androgen overproduction.

Area of Application: PCOS

PCOS (affects ~10% of women of childbearing age) is associated with insulin resistance, elevated androgens, and menstrual cycle disorders. Inositol supplementation:

Parameter in PCOS	Effect with Myo-Inositol	Evidence
Insulin resistance	Significantly improved	Several RCTs
Androgen levels (testosterone, DHEAS)	Reduced	Well-documented
Menstrual regularity	Improved (more ovulatory cycles)	Well-documented
Fertility	Improved egg quality and pregnancy rates	Well-documented
LH/FSH ratio	Normalized	Moderate

The optimal ratio for PCOS: Myo-Inositol 40:1 D-Chiro-Inositol (e.g., 4,000 mg MI + 100 mg DCI daily).

Further Applications

Panic Disorder/OCD: 12–18 g/day MI showed efficacy comparable to fluvoxamine (SSRI) in several studies
Depression: 12 g/day; modulates serotonin signaling (PI cycle)
Gestational Diabetes: Myo-inositol reduces the risk of gestational diabetes in at-risk groups
Lithium Mechanism: Lithium (for bipolar disorders) acts partly through inositol depletion

Dosage

Application	Dose	Form
PCOS	4,000 mg MI + 100 mg DCI daily	Divided into 2 doses
Mental Health	12–18 g MI daily	Powder form often necessary
General Insulin Sensitivity	2,000–4,000 mg MI	Daily with meal

Frequently Asked Questions (FAQ)

Is inositol safe during pregnancy?

Myo-inositol is used in studies for the prevention of gestational diabetes and neural tube defects (combined with folic acid) – with a good safety record. Nevertheless, always consult a doctor.

How long until effect in PCOS?

Initial cycle improvements often after 2–3 months. Full normalization of hormone levels after 3–6 months with consistent intake.