Hypothyroidism and hyperthyroidism are two common forms of thyroid diseases, which – if left unmanaged – can make daily living quite challenging. Hypothyroidism is also known as an underactive thyroid, meaning the thyroid doesn’t produce enough hormones, thus slowing down bodily functions. In hyperthyroidism – overactive thyroid – the thyroid overproduces thyroid hormones, which in turn speed up bodily functions.
Hypothyroidism is a long-term health problem that needs to be managed throughout a person’s life. In hyperthyroidism, some cases may be temporary if they are a result of pregnancy or an autoimmune disease known as Grave’s disease, which does not have a cure.
Although both conditions affect the thyroid, they are two different diseases and so it’s important to understand their differences.
The biggest difference between hypothyroidism and hyperthyroidism is hormone levels. In hypothyroidism, hormone levels are low, and in hyperthyroidism hormone levels are high.
Another difference is the cause of either condition. For hypothyroidism, the most common cause is Hashimoto’s disease, and in hyperthyroidism the common cause is Grave’s disease. Both diseases are autoimmune, which means the immune system mistakenly attacks itself, leading to malfunctions of the thyroid gland.
Other differences between hypothyroidism and hyperthyroidism are in the symptoms. Either condition can affect the body in its own unique ways, so the below chart outlines these differences within the body.
|Body weight||Weight gain||Weight loss|
|Temperature sensitivity||Intolerant to cold||Intolerant to heat|
|Heart rate||Slow heart rate (bradycardia)||Fast heart rate (tachycardia)|
|Blood pressure||Hypertension or hypotension||Hypertension|
|Sexual/reproductive functioning||Infertility, loss of libido, and erectile dysfunction||Infertility, loss of libido, erectile dysfunction, and spontaneous abortion|
|Energy levels||Low energy, fatigue, sleepiness||Fatigued but hyperactive – cannot sit still|
|Mental state||Depression, poor memory, and inability to concentrate||Anxious, irritable, and nervous|
|Fluid accumulation||Leg, hands, eyelid swelling, fluid around the lungs (pleural effusion) and heart (pericardial effusion), abdominal swelling,round, puffy face||Ankle swelling, feet and toes may also be swollen|
|Skin and hair||Dry, pale skin, coarse, dry hair, purple-tinged lips, itchy skin, hair loss, loss of lateral eyebrow, red rash with lines of hyperpigmentation||Sweaty skin, warm and smooth skin, thinning skin, pigmentation, itchy skin, hair loss, redness of palms|
|Reflexes||Delayed relaxation of reflexes||Overactive reflexes|
|Menstrual cycles||Heavy flow and prolonged or frequent periods||Light flow with absent or infrequent periods|
|Muscle and movements||Muscle stiffness, slow to relax, aches and pains||Tremors and muscle weakness|
There are times when both hyperthyroidism and hypothyroidism can occur together. In the first instance, treatment of one thyroid disease can contribute to the onset of another, and in the second instance an autoimmune disease can be responsible for both.
Minisha Sood, MD, an endocrinologist at Lenox Hill Hospital in New York City, explained the first instance, “Sometimes a person has hypothyroidism and is treated with too much thyroid hormone and may start to develop symptoms of hyperthyroidism, such as weight loss, rapid heart beat, sweatiness, and shakiness.” On the other hand, aggressive treatment of hyperthyroidism can lead to hypothyroidism.
In instance two, antibodies from one autoimmune disease that commonly leads to thyroid disease – Grave’s disease or Hashimoto’s disease – can trigger antibodies for the other autoimmune disease, thus contributing to both thyroid diseases. Although both diseases cannot occur at the same time, an individual with autoimmune-mediated thyroid diseases may go about their life switching from hypothyroidism to hyperthyroidism and vice versa.
Doctors suggest that when you begin to notice a switch in your symptoms either from fast to slow or slow to fast, go get yourself checked right away before complications can occur.