- Fatigue, irritability, feeling cold, and constipation may be signs of a thyroid condition.
- Iodine can be a problem whether deficient or excessive. In particular, be careful not to overdo kombu dashi and seaweed.
- Excessive intake of soy products can affect the thyroid, so balance is important.
- Selenium helps support thyroid function, but excessive supplement intake is dangerous.
- Don't rely on self-diagnosis; if you have concerns, please get a blood test such as TSH and Free T4 at a medical facility.
Introduction: Easy fatigue and irritability... those could be signs of a thyroid issue.
"Recently, you’ve been unusually tired," "irritable for no reason," "gaining or losing weight without a change on the scale" — these vague symptoms can be caused by hormonal imbalances, especially abnormalities in thyroid hormones. Thyroid diseases are often overlooked because their symptoms overlap with other conditions. We have also seen cases among people around us who were told "no known cause" and improved after thyroid testing, and we feel that early detection is important.
What is thyroid disease? What symptoms does it cause?
Thyroid function and the typical symptoms that can arise
The thyroid is a small organ at the front of the neck that produces hormones such as T3 (triiodothyronine) and T4 (thyroxine), and it influences metabolism, body temperature, heart rate, brain function, digestion, and mood stability. In hyperthyroidism (overproduction of thyroid hormones), palpitations, anxiety, insomnia, weight loss, muscle weakness, and eye symptoms tend to appear. Conversely, in hypothyroidism (underproduction), fatigue, cold intolerance, constipation, weight gain, memory impairment, and menstrual irregularities can occur. These can easily be mistaken for everyday issues, so confirmation with specialized blood tests is important. (Guidelines from the Japanese Thyroid Association and medical institutions also emphasize the importance of testing.)
Causes and nutrients to watch out for in particular: iodine, soy, selenium
The balance of iodine is important
Iodine is a raw material for thyroid hormones, and in Japan, due to the seaweed-rich dietary culture, it is usually possible to obtain enough. However, iodine deficiency can lead to thyroid hormone deficiency, and conversely, excess can also disrupt thyroid function. In particular, kombu (kelp) and dried wakame are high in iodine, and we can end up consuming quite a bit through dashi stock or furikake. When we actually checked our eating habits, we felt that households that use kombu dashi every day should be mindful.
Soy (isoflavones) and thyroid health
Isoflavones and goitrogenic compounds found in soy may theoretically affect thyroid hormone synthesis and iodine uptake. Everyday soy foods (tofu, natto, miso, etc.) also have health benefits, so there is no need to avoid them entirely, but if you have a habit of consuming large amounts daily, we recommend reassessing the balance.
Selenium is helpful in moderation
Selenium is a nutrient involved in the metabolism of thyroid hormones, and selenium deficiency is thought to potentially influence the course of thyroid disease. However, taking selenium supplements in excess carries risks of toxicity and side effects, so the basic approach is to obtain it in moderation from foods such as fish, seafood, meat, and eggs. There are studies and clinical reports, but please consult a doctor before starting supplements.
Practical daily checks and concrete lifestyle measures
Self-checks and when to seek medical care
• Neck swelling or a lump, or a sense of pressure in the neck
- Persistent insomnia, palpitations, unusual weight changes, chronic fatigue and constipation, and feeling cold.
- If these symptoms persist, please undergo TSH, Free T4, and, if necessary, antibody tests at internal medicine or endocrinology. The tests can be easily performed with a blood test.
- Practical tips for diet and lifestyle
- Limit seaweed to a few times a week, and dilute dashi to avoid iodine excess.
- To avoid over-reliance on soy products in a day, pair them with other protein sources (fish, meat, eggs).
Selenium is obtained from seafood, meat, and eggs. If you're considering supplements, consult a physician.
Make a point of moderate exercise, regular sleep, and stress management.
We, too, have found that small adjustments to our eating habits can stabilize how we feel, and we recommend changes that are easy to sustain.
How do tests and treatments progress? Early consultation is essential.
Treatment for thyroid disorders depends on the cause and type, and may include pharmacotherapy, radiation therapy, or surgery. In many cases, it can be controlled with oral medications, with regular blood tests to monitor the effects and side effects of the medications. Because it can affect the heart (such as tachycardia, arrhythmias, or worsening blood lipid levels), treatment coordinated with a cardiologist may be important. Do not restrict nutrients excessively on your own or start large amounts of supplements; please consult a medical specialist.
Summary
Fatigue, irritability, and vague changes in weight or bowel movements can sometimes be caused by thyroid disorders. Because both iodine deficiency and excess can cause problems, it’s important to watch how you include seaweed in your diet and to balance your intake of soybeans and selenium. If the concerning symptoms persist, first check your thyroid hormone levels with a blood test, and adjust your lifestyle in consultation with a doctor. We, too, have felt our health improve with small lifestyle changes, and we recommend taking an early step.
Disclaimer: The information in this article is for general informational purposes only and does not constitute medical advice. Please consult a qualified healthcare professional before making any health-related decisions.