Thyroid Health and Digestion: The Surprising Gut Connection

Your small intestine and colon form a long, continuous tube in your body, and their function is crucial for digestion and nutrient absorption. The digestive process relies on a rhythmic contraction of the muscles in the digestive tract, known as peristalsis. This wave-like movement helps push undigested food through your intestines, allowing your body to absorb nutrients and expel waste. Thyroid hormones play a key role in regulating the speed and efficiency of peristalsis.

When you have hypothyroidism (an underactive thyroid), peristalsis becomes slower, which leads to sluggish digestion. This slowdown can result in constipation, as food takes longer to move through your intestines. Additionally, because food stays in the intestines longer, your body may absorb more calories than usual, leading to weight gain even if your diet hasn’t changed. The slower digestion also means that toxins and waste products, which should normally be eliminated quickly, remain in your system for a longer period. This can increase your exposure to harmful substances and contribute to feelings of fatigue or discomfort.

Conversely, with hyperthyroidism (an overactive thyroid), peristalsis speeds up, causing food to pass through the digestive tract too quickly. This rapid movement can result in frequent bowel movements or loose stools, as the food doesn’t stay in the intestines long enough for proper nutrient absorption. As a result, you may experience weight loss despite eating the same amount of food, as fewer calories are absorbed into your body.

While occasional constipation or loose stools can occur for a variety of reasons, if these digestive issues persist and there is no clear cause, it is worth considering whether thyroid dysfunction might be at the root. Understanding the link between thyroid health and digestive function can help identify if a thyroid condition is contributing to these symptoms.