Thyroxine Side Effects

thyroxine side effectsWhat Is Thyroxine

Thyroxine is one of the hormones generated by the thyroid gland. It’s also abbreviated T4. Thyroxine along with triiodothyronine (T3) have more or less of an influence upon all the cells in the body. Their main effect is to increase the basal metabolic rate, or in other words, to increase the total number of chemical processes that take place in the body.

Thyroxine Beneficial Effects

Thyroxine has as main effects the augmentation of the metabolism of carbohydrates and proteins, increases the metabolic rate, it increases heart rate and cardiac output, stimulates brain development for the growth period of a human. It has a role in thickening the inner membrane (endometrium) of the uterus, and stimulates the activity of the sympathetic nervous system by potentiating the catecholamines.

One of the most important compounds for the production of thyroid hormones is iodine. The lack of iodine in the system may lead to a low level of T3 and T4 hormones, which causes goitre (an abnormal increase of the thyroid tissue).

There aren’t any plants, or foods that naturally contain thyroxine, only foods that contain various compounds that may boost the activity of the thyroid gland. For example, plants with a high concentration of iodine, like kelp or seaweed, can be consumed in case of a sluggish thyroid gland. For patients that have a naturally under-active thyroid gland, or the natural emission of thyroxine in the body is blocked by various conditions, thyroxine can be administered as a supplement. The thyroxine supplement is called levothyroxine, or L-thyroxine.

Thyroxine Side Effects

Thyroxine is a hormone naturally produced in the human body, and there aren’t actually any side effects associated with it. The only so-called thyroxine side effects can result from a deficiency or an increased amount of thyroxine. So, here are the thyroxine side effects related to each of the conditions mentioned.


The thyroxine side effects in case of hypothyroidism (low thyroxine level) are all connected to the slow metabolic rate. These are: fatigue, low heart rate, constipation, depression, joint and muscle pain, low muscle tone, decreased or no sweating at all, edema, weight gain, sensitivity to cold, infertility, menstrual cycle disorders, high cholesterol levels, dry skin, galactorrhea and hyperprolactinemia.

Other, uncommon thyroxine side effects that may occur due to the low level of this hormone are: hair loss, difficulties breathing and swallowing, somnolence, mood changes, decreased reflexes, vitamin A intoxication, anemia, hypoglycemia, decreased sense of smell and taste, decreased libido, decreased renal function.


Thyroxine side effects in case of hyperthyroidism are associated with an increased metabolic rate. Hyperthyroidism has the following symptoms: nervousness, excessive sweating, increased heart rate and palpitations, insomnia, hand tremors, increased bowel movements, heat intolerance, weight loss, muscle pain and myopathy.

One of the increased thyroxine side effects is Graves diseases (eyes look larger due to the fact that eye muscles swell, pushing eyes forward).

In women, hyperthyroidism may cause a light menstrual flow, and may even reduce menstrual cycle. On the other hand, in men it may cause gynaecomastia (enlargement of mammary glands) and feminization. Hyperthyroidism can also cause osteoporosis.

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