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Every gland in your endocrine system has a direct effect on other glands. In addition to the thyroid gland, your endocrine system includes the hypothalamus, pineal gland, pituitary gland, parathyroid glands, thymus, adrenal glands, pancreas, and the testes in males and ovaries in females. These glands create hormones that support various functions in your body, including metabolism, digestion, growth and development, emotions and mood, fertility and sexual function, sleep, and blood pressure. The endocrine system also works closely with other body systems, including the immune system. As part of the complex interaction between the endocrine and immune systems, one chemical in particular -- histamine -- plays a key role. Ahead, a look at the connection between histamine, histamine intolerance, and your thyroid.
Similar to thyroid hormones, histamine helps direct various functions in your body. In the stomach, histamine controls the production of hydrochloric acid (called H2 receptors); in the nervous system, histamine acts as a neurotransmitter transferring messages about our sleep and behavior throughout the brain (called H3 receptors). Histamine receptors (H4 receptors) are also found in the colon, liver, lungs, small intestine, thymus, spleen, testes, tonsils, and trachea.
Histamine is released by specialized white blood cells called mast cells. The histamine causes blood vessels to widen and become leaky, which explains histamine’s ability to create allergic reactions. The symptoms experienced during an allergic reaction or even when experiencing seasonal allergies are histamine’s way of protecting you from allergens. However, when excess amounts of histamine are released, it can trigger other health effects and affect your thyroid.
Some people have a condition known as histamine intolerance, where the body consistently produces too much histamine, or there’s a reduced ability to break down histamine, leading to over accumulation. When you cannot metabolize histamine properly and continue to eat histamine-rich foods, it can cause an immune response and worsen allergy symptoms. This, in turn, can negatively affect your thyroid.
Histamine intolerance can impact autoimmune diseases, including Hashimoto’s thyroiditis. Research suggests that histamine intolerance may contribute to developing or exacerbating autoimmune diseases, particularly those involving inflammation.
Histamine is a potent immune system mediator and can trigger the release of other pro-inflammatory molecules in the body. If you have an autoimmune disease, this excess inflammation can worsen symptoms and damage tissue.
Additionally, histamine can also affect the permeability of the gut lining, allowing for the increased passage of undigested food particles and other substances into the bloodstream. A permeable “leaky gut ” can lead to autoimmune reactions, where the immune system attacks these foreign substances and mistakenly attacks the body’s own tissues.
Furthermore, histamine can activate mast cells, immune cells crucial in allergic and inflammatory reactions. Mast cells are also involved in the development and progression of autoimmune diseases, and their activation by histamine can contribute to autoimmune-related symptoms.
Overall, histamine intolerance can contribute to the development or worsening of autoimmune disease through its effects on inflammation, gut permeability, and mast cell activation.
As discussed, mast cells release histamine during the onset of an allergic reaction. Interestingly, mast cells also store some thyroid hormones, meaning that when they release histamine, they release some thyroid hormones.
Histamine can affect the thyroid gland in several ways. When histamine is released in response to an immune challenge or allergen, it can cause inflammation and increase blood flow to the affected area. In the thyroid gland, this can lead to an increase in the size of the gland, a condition called goiter, as well as damage to thyroid tissue. Ultimately, reduced thyroid function and the development of hypothyroidism can result.
Histamine can interfere with thyroid hormone production by inhibiting the enzyme’s activity that converts thyroxine (T4) to the active form of thyroid hormone, triiodothyronine (T3). As a result, T3 can decrease, which can also contribute to the development of hypothyroidism and worsening symptoms.
In addition, high levels of histamine can affect gut health and impair the absorption of thyroid hormones by the body, which can further exacerbate the adverse effects on thyroid function.
Histamine also interferes with the uptake of iodine, the essential nutrient required for synthesizing thyroid hormones. Histamine can compete with iodine for uptake into the thyroid gland, reducing thyroid hormone production. This reduction is particularly relevant for individuals with iodine deficiency or those on a low-iodine diet.
Finally, histamine can affect the synthesis and release of thyroid hormones. Studies have shown that histamine can stimulate the release of thyroid-stimulating hormone (TSH) from the pituitary gland, which in turn can stimulate the production and release of thyroid hormones from the thyroid gland, leading to an abnormal increase in thyroid hormone production and hyperthyroidism.
Histamine intolerance is not a well-defined medical condition; the symptoms can be similar to other conditions, such as allergies or food sensitivities. Diagnosis can be difficult, and no standard histamine intolerance test exists. Diagnosis usually relies on symptoms.
The challenge is that the symptoms of histamine intolerance are fairly extensive, affecting organs and even tissues of the body, and some are common in many other conditions. Most frequently, people with histamine intolerance experience gastrointestinal symptoms such as bloating, nausea, diarrhea, abdominal pain, and constipation. The nervous and cardiovascular systems might produce symptoms such as dizziness, headaches, and palpitations. Respiratory symptoms include nasal congestion, sneezing, and dermatological symptoms, including flush, urticaria, eczema, and swelling.
When histamine intolerance is suspected, the treatment is typically to eat foods low in histamine until the overall concern (such as gut imbalances or excess inflammation) are addressed. In addition to avoiding high-histamine foods listed below, vitamins B6 and C have both been shown to reduce symptoms of histamine intolerance. Quercetin also has been shown to block excess histamine release.
If you suffer from histamine intolerance, consider the two lists below. If you’re more prone to seasonal allergies, for example, try to incorporate more low-histamine foods and be wary of not overconsuming high-histamine foods.
High histamine foods include:
- Eggplant, tomatoes, and spinach
- Pickled or fermented foods
- Matured cheeses
- Smoked meat products
- Long stored nuts
Low histamine foods include:
- Grass-fed meat and poultry
- Wild-caught fish
- Fruits and vegetables (except for those listed under high-histamine foods)
- Pasteurized dairy, including cow, goat, and sheep products
- Herbal teas
Proper treatment and management of hypothyroidism require knowing your thyroid hormone levels. Paloma offers a convenient and affordable at-home thyroid test kit that measures TSH, Free T4, Free T3, and Thyroid Peroxidase Antibodies (TPOAb). You can also choose to add on a Reverse T3 and/or Vitamin D test. For optimal thyroid care, consider working with a Paloma Health practitioner who can help you understand your results and oversee your personalized -- and effective -- treatment plan for an underactive thyroid. Virtual visits with top thyroid doctors are available from the comfort of your home.