Citicoline, also known as CDP-choline, is an endogenous compound and a precursor in the synthesis of phosphatidylcholine, a crucial component of cell membranes. In supplement form, it is widely used for its nootropic (cognitive-enhancing) and neuroprotective benefits, particularly in conditions like stroke and age-related cognitive decline. While research into its brain-related effects is extensive, its specific impact on the thyroid gland and hormone regulation is less understood in humans. The current evidence, largely from animal models, suggests a complex and indirect relationship, particularly under conditions of physiological stress.
Evidence from Animal Studies on Citicoline and Thyroid Function
Most of the direct evidence linking citicoline to thyroid modulation comes from animal research, often involving induced conditions. These studies provide valuable insights but are not definitive for human physiology. Two key studies illustrate this relationship:
Radiation-Induced Liver and Thyroid Disturbances
A recent 2025 study in rats exposed to gamma-radiation investigated citicoline's protective effects. The radiation significantly reduced serum thyroid hormones (T3 and T4) and altered other related markers. The study found that treatment with citicoline improved several of these metrics:
- Increased T3 levels: Citicoline significantly raised serum triiodothyronine (T3) levels in the irradiated rats.
- Modulated enzyme activity: It improved the activity of iodothyronine deiodinase type 1 (D1) in hepatic tissues, an enzyme crucial for converting T4 to the more active T3.
- Affected gene expression: Citicoline also increased the gene expression of the thyroid hormone receptor beta (TRβ).
These findings suggest that citicoline can modulate thyroid hormone metabolism, particularly in a context of severe oxidative stress and inflammation affecting the liver.
Cardioprotection in Hyperthyroid Rats
Another animal study focused on hyperthyroid rats with induced mitochondrial dysfunction. In this model, citicoline was shown to protect against heart damage resulting from reperfusion injury. The researchers concluded that citicoline helped preserve mitochondrial function in the hearts of hyperthyroid rats, a mechanism that could help alleviate some of the cardiovascular symptoms associated with hyperthyroidism. This does not mean citicoline treats hyperthyroidism but rather offers a protective effect on a specific organ impacted by the condition.
Potential Endocrine System Interactions
Beyond its effect on peripheral hormone metabolism, citicoline also interacts with the central nervous system, which in turn influences endocrine function. Research indicates that citicoline can activate the central cholinergic system, which can have ripple effects on hormone regulation.
- Potentiation of TSH levels: By stimulating the cholinergic system, citicoline has been shown to potentiate serum thyroid-stimulating hormone (TSH) levels. This is not a direct stimulation of the thyroid gland itself but an effect mediated via the pituitary gland's control over thyroid function.
- HPA axis influence: Citicoline's influence extends to other hormonal pathways, including the hypothalamic-pituitary-adrenal (HPA) axis, with evidence of increased adrenocorticotropic hormone (ACTH) levels.
The Clinical Implications for Humans
It is critical to note that the findings from animal models and indirect central nervous system interactions do not necessarily translate to a significant impact on thyroid health in humans. The effects observed in these studies, particularly those involving induced conditions, are not the same as a treatment for or cause of a thyroid disease. There is currently no robust human clinical trial data indicating that citicoline can treat or cure thyroid disorders or that it poses a significant risk to normal thyroid function.
Individuals with existing thyroid conditions, such as hyperthyroidism or hypothyroidism, should exercise caution. Modulating TSH levels, even indirectly, could potentially interfere with the delicate balance maintained by their prescribed medication. As with any new supplement, consultation with a healthcare provider is essential, especially for those with pre-existing endocrine conditions.
Citicoline vs. Conventional Thyroid Medication
For clarity, it is useful to compare citicoline with standard treatments for thyroid disease.
| Feature | Citicoline | Thyroid Medication (e.g., Levothyroxine) |
|---|---|---|
| Primary Use | Nootropic, neuroprotective agent, cognitive support. | Restores thyroid hormone levels in individuals with hypothyroidism. |
| Mechanism of Action | Provides choline and cytidine for phospholipid synthesis and neurotransmitter production. Indirectly affects TSH and modulates thyroid hormone metabolism in specific contexts. | Directly replaces the missing thyroid hormone (T4) that the body is not producing adequately. |
| Effect on Thyroid Hormones | May modulate levels under stress in animal models but does not consistently regulate hormones in healthy humans. | Directly corrects T4 and TSH levels to a normal range. |
| Regulation | Sold as a dietary supplement in the U.S., with varying regulatory oversight. | A prescription medication, strictly regulated and monitored by a physician. |
| Safety Profile | Generally well-tolerated with mild side effects (headache, GI issues). Not recommended for pregnant/breastfeeding women. | Side effects are possible, particularly if the dose is incorrect, leading to symptoms of hyper- or hypothyroidism. |
Factors Influencing Thyroid Health
- Iodine intake: The thyroid gland requires adequate iodine to produce hormones. Both deficiency and excess can cause problems.
- Nutrient deficiencies: Deficiencies in selenium, zinc, and iron can impact thyroid function and hormone conversion.
- Stress: Chronic stress can disrupt the HPA axis, which is intricately linked to the thyroid axis.
- Environmental toxins: Exposure to radiation and certain chemicals can negatively affect the thyroid.
- Genetics: Predisposition to autoimmune diseases like Hashimoto's thyroiditis or Graves' disease can be genetic.
- Other medications: Certain drugs can interfere with thyroid hormone levels or absorption. It is crucial to discuss all medications and supplements with a doctor.
Conclusion
The existing research suggests that citicoline is not a direct treatment for thyroid disease, nor is there significant evidence to indicate it causes thyroid dysfunction in humans. While animal studies show it can modulate thyroid hormone metabolism and potentiate TSH levels under specific conditions, these effects are largely indirect and stress-dependent. For individuals with a diagnosed thyroid condition, the potential for interactions, even indirect ones, necessitates a cautious approach and consultation with a healthcare provider before beginning a citicoline regimen. While generally safe, the lack of human-specific data on this interaction warrants ongoing monitoring for anyone concerned about how supplements like citicoline might affect their endocrine health.
For more detailed information on citicoline's neuroprotective actions in experimental models, consult this review on the role of citicoline in neuroprotection from the National Institutes of Health.
