Thyroid and Weight

An unexplained change in weight is a common symptom of a thyroid disorder. The thyroid is a small butterfly-shaped gland in the front of your neck. Working together with the pituitary gland, the thyroid’s job is to make thyroid hormones that are carried to every part of the body. The thyroid is central to metabolism, growth, and development of the human body. While thyroid hormone can impact basal metabolic rate (BMR), metabolism and weight gain are multifactorial.

It has been known for a long time that there is a complex relationship between thyroid, metabolism, and body weight. Our pituitary gland makes a hormone called Thyroid Stimulating Hormone (TSH), which tells the thyroid gland whether to release more or less thyroid hormone (T3 and T4) into the blood stream.  T3 and T4 increase the basal metabolic rate and leads to an increase in body temperature, a faster pulse, faster energy consumption, and an increase in growth (in children).  When T3 and T4 levels drop, there is a signal to the pituitary to increase production of TSH, which will lead to increased stimulation of the thyroid gland to make more thyroid hormone.

There are two types of thyroid conditions that can impact weight.

• Hyperthyroidism (Overactive Thyroid) is when the thyroid gland is producing too much thyroid hormone, which can lead to weight loss. The most common cause of hyperthyroidism is Graves’ disease. Graves’ is an autoimmune disorder that attacks the thyroid gland and triggers the release of high levels of thyroid hormones. Some other causes include ‘toxic’ thyroid nodules, inflammation of the thyroid (thyroiditis), and taking excess thyroid hormone.
• Hypothyroidism (Underactive Thyroid) or an underactive thyroid occurs when the body produces too little thyroid hormone, which can often lead to weight gain. The most common cause of hypothyroidism is Hashimoto's disease.  Hashimoto’s is an autoimmune disorder where the body makes antibodies that attack the thyroid gland, resulting in damage that prevents it from producing enough hormones. Hypothyroidism can also be caused by a pituitary issue, a temporary inflammation of the thyroid, or medications that impact thyroid function.

Signs & Symptoms of Hyperthyroidism: 

• Sudden weight loss,
• Rapid heartbeat (tachycardia), irregular heartbeat or palpitations,
• Increased appetite,
• Nervousness, anxiety, and irritability,
• Trouble sleeping,
• Tremor,
• Sweating,
• Changes in menstrual cycle,
• Heat sensitivity,
• Changes in bowel patterns,
• An enlarged thyroid gland or swelling at the base of your neck,
• Fatigue and muscle weakness.

Signs & Symptoms of Hypothyroidism:

• Fatigue,
• Cold sensitivity,
• Constipation,
• Pale, dry skin,
• Puffy face,
• Elevated cholesterol,
• Unexplained weight gain,
• Muscle aches, tenderness, and stiffness,
• Joint pain, swelling, or stiffness,
• Brittle fingernails and hair,
• Depression.

If you are worried about your thyroid, please discuss it with your doctor. Most doctors start a thyroid evaluation with a simple blood test measuring the TSH (the pituitary hormone).  If TSH is high, it typically means that your thyroid function is low (hypothyroid). If the TSH is low, then it usually means the thyroid is overactive (hyperthyroidism). After this screening test, your doctor may want to check additional thyroid lab tests or consider a referral to an endocrinologist.

DISCLAIMER: Sarah Smith MD is a medical doctor, but she is not your doctor, and she is not offering medical advice on this website. If you are in need of professional advice or medical care, you must seek out the services of your own doctor or health care professional.