What is the relationship between the thyroid and the immune system?
There is a clear and well-defined relationship: autoimmune diseases of the thyroid arise because the immune system attacks the thyroid. Whether you have an underactive or an overactive thyroid, the type of immune response determines the difference.
Autoimmune thyroid diseases are the most common organ-specific autoimmune diseases; the estimated prevalence is around 5%, but antibodies against the thyroid are even more widespread. Women are affected more often than men, probably due to sex hormones and hereditary factors on the X chromosome. The two best-known forms are Hashimoto's disease (underactive thyroid) and Graves' disease (overactive thyroid).
The core of the problem is that the immune system begins to treat the thyroid as an enemy. Immune cells invade thyroid tissue and produce antibodies against thyroid proteins. In Hashimoto's disease, this destroys the tissue, causing the thyroid to produce too little hormone. In Graves' disease, specific antibodies instead make the thyroid overactive by mimicking the receptor that normally regulates the hormone. Blocking variants of those same antibodies can also cause an underactive thyroid.
What keeps this process going is a self-reinforcing chain of inflammatory signals. Th1 immune cells trigger responses that prompt thyroid cells to produce more inflammatory substances, which in turn attract new immune cells. Tissue studies in Hashimoto's patients also show that supporting cells within the thyroid itself actively recruit immune cells, and that mini lymph nodes can form in thyroid tissue that amplify the inflammation. This has been found in human tissue, but these are not yet proven mechanisms in large clinical studies.
The relationship also works in the other direction: during pregnancy, a different type of immune response predominates, which helps the body tolerate the child. After delivery, this balance shifts back, which in some women leads to temporary thyroid inflammation. Furthermore, certain immune cells themselves appear to produce the hormone that normally directs the thyroid from the brain, although the practical significance of this is still unclear.
A minority of Hashimoto's patients continue to experience symptoms even after hormone levels have been corrected with medication. Reviews suggest that the autoimmune process itself may be responsible for this, but that remains a hypothesis. People with autoimmune thyroid disease also have a somewhat higher risk of other autoimmune diseases, such as rheumatoid arthritis or lupus. There is a possible link with a particular type of thyroid cancer, but this is still a matter of debate.
All claims are based on reviews (including several broad overview studies). There are no randomised trials or meta-analyses among the sources. The tissue data on stromal cells and macrophages in Hashimoto's come from one non-further-indexed study using single-cell tissue analysis.
Does creatine do anything to your immune system?
Creatine affects immune cells, but whether that turns out well or badly depends strongly on the situation. For healthy older adults who also do strength training there is a cautiously positive signal; if you have endometriosis or a certain type of cancer, the context is more complex and consulting your doctor is advisable.
What does alcohol do to your immune system?
Chronic excessive alcohol use weakens your immune system on multiple fronts simultaneously and increases the risk of serious infections. Light to moderate drinking appears less harmful, but offers no demonstrable benefit for your immune system.
Does your immune system really weaken as you get older?
Your immune system does indeed weaken as you get older, but how quickly that happens varies considerably from person to person. Lifestyle factors play a role in this, although little has yet been proven specifically for humans.
Does too little sleep weaken your immune system?
Yes, too little sleep demonstrably weakens your immune system and increases the risk of infections and chronic inflammatory conditions. Seven to nine hours of sleep is the most commonly cited guideline, and vaccinations also work better when you are well rested.
Does eating enough protein help my immune system as I get older?
Eating enough protein helps your immune system in later life. Aim for at least 1.0-1.2 grams per kilogram of body weight per day, spread across your meals, and preferably obtain this from ordinary food rather than supplements.
Does melatonin support your immune system in later life?
Melatonin has clear effects on the immune system in animal and laboratory research, but whether supplements genuinely improve immune function in older people has not yet been demonstrated. It has long been used for better sleep, which may be indirectly beneficial.