When it comes to weight, most people think about calories, exercise, and lifestyle habits.
However, there is another important factor that can affect the number on the scale: Thyroid disorders are common medical conditions that occur when the thyroid gland, which is located in the neck and shaped like a butterfly, produces too much or too little hormone, thereby disrupting the body's metabolism.
As the thyroid controls how cells use energy, malfunctions can affect nearly every major organ, including the heart, brain and skin. An underactive gland slows the body's systems down, while an overactive gland forces them into overdrive.
Fortunately, most thyroid imbalances can be easily diagnosed through simple blood tests and are well managed with proper medical treatment.
According to Dr Josephine Okwoyo, thyroid disorders occur when the butterfly-shaped gland in the neck produces too much or too little hormone, affecting how the body uses energy.
The thyroid produces hormones, mainly thyroxine (T4) and triiodothyronine (T3), which help regulate metabolism, body temperature, heart rate, digestion and energy use. T3 is the more active form, and changes in thyroid hormone levels can affect metabolism and, in some cases, body weight.
An underactive thyroid, known as hypothyroidism, occurs when the gland produces insufficient hormones. This can slow the body’s energy expenditure and contribute to weight gain, although thyroid-related weight gain is generally modest and does not explain obesity on its own.
Dr Josephine Okwoyo says that people should not automatically attribute every unexplained increase in weight to thyroid disease.
“Not every case of weight gain is caused by the thyroid. Thyroid dysfunction can contribute to weight changes, but it is important to investigate other possible causes as well,” she adds.
According to Dr Okwoyo, common symptoms of an underactive thyroid include persistent tiredness, unexplained weight gain, sensitivity to cold, dry skin, constipation, muscle or joint pain, low mood, difficulty concentrating and menstrual changes. Some people may also experience thinning hair, a slower heart rate and facial puffiness.
Hypothyroidism has several possible causes, with Hashimoto's thyroiditis, an autoimmune condition in which the immune system attacks the thyroid, being one of the most common. Other causes include iodine imbalance, certain medications, previous thyroid surgery or radioactive iodine treatment, and pituitary disorders.
Dr Okwoyo says an overactive thyroid can have almost the opposite effect on metabolism. Excess thyroid hormones increase energy expenditure and can cause unexplained weight loss, sometimes even when a person is eating normally or has an increased appetite.
“Thyroid hormones affect virtually every organ system, so an imbalance can present with several symptoms beyond weight changes,” Dr Okwoyo explains.
Other symptoms of hyperthyroidism can include rapid or irregular heartbeat, excessive sweating, heat intolerance, anxiety, irritability, tremors, difficulty sleeping, frequent bowel movements and muscle weakness.
Some people develop an enlarged thyroid, known as a goitre, while those with Graves’ disease may experience eye-related symptoms.
Dr Okwoyo says weight changes alone do not confirm thyroid disease, as many factors can affect weight. Thyroid function is assessed through tests such as TSH and free T4, while hypothyroidism is treated with hormone replacement.
Unexplained weight changes should be medically assessed rather than self-treated with thyroid medication.