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Thyroxine is an important hormone in the body - but how much is too much and how much is too little? Find out the effects of having too much or too little Thyroxine in the body.

The thyroid hormone thyroxine is also called T4 and is scientifically known as 3, 5, 3’5,’-tetraiodothyronine. It is a hormone produced by the thyroid gland and is a very important hormone in the body.

The function of thyroxine involves the stimulation of oxygen consumption which leads to tissue and cellular metabolism. Along with that, it is used as a biochemical indicator of the functioning of the thyroid gland. This helps in the monitoring and diagnosing problems related to the thyroid gland itself.

In addition to that, the hormone plays an important role in the regulation of the heart and digestive functions, bone maintenance, brain development, muscle control as well as the metabolic rate of the body. Thyroxine is also converted by the kidney and the liver and turned to other kinds of hormones.

Because it plays such an important role in numerous functions of the body, having too much or too little of the thyroid hormone can cause problems in the body.

When the thyroid gland produces excess thyroxine, the individual may suffer from hyperthyroidism. When a person is deficient with this kind of hormone, on the other hand, he or she will suffer from hypothyroidism.

Hypothyroidism and hyperthyroidism are two different kinds of thyroid conditions that exhibit different kinds of symptoms. Still, both conditions can make life difficult for the patient.

Thyroxine Hormonal Level

Acceptable level

The normal acceptable level of thyroxine is in between 4.5 micrograms to 11.2 micrograms per deciliter of blood. If the amount of thyroxine hormone falls lower than 4.5 micrograms of thyroxine per deciliter of blood is considered low level, and if the amount is higher than 11.2 micrograms per deciliter of blood, then that is considered high level.

Thyroid Hormone Level Guide
Low level - Less than 4.5 mcg/deciliter of blood
Acceptable level - 4.5 to 11.2 mcg/deciliter of blood
High level - More than 11.2 mcg/deciliter of blood

Low Thyroxine Hormone Level

When thyroxine level falls lower than the acceptable level, the person may start to manifest symptoms of hypothyroidism. Low levels of thyroid hormones are caused by the underactive thyroid gland, and the symptoms usually are:

  • Dry, cool skin
  • Loss of concentration
  • White patches in the skin
  • Brittle hair
  • Weak nails
  • Heavy menstruation
  • Slow pulse
  • Tiredness
  • Ringing of ears
  • Joint pain
  • Weakness
  • Muscle pain
  • Slow speech
  • Slow reflexes
  • Constipation 
  • Insomnia
  • Enlarged heart
  • Decrease of libido
  • Intolerance to cold

Aside from that, people who have hypothyroidism may experience changes in their metabolism which may lead to weight gain and other medical conditions such as an increase in the levels of bad cholesterol or LDL cholesterol, increased risk for hypertension, stroke, heart attack.

Women with hypothyroidism may also experience problems during the pregnancy and may have a high risk of miscarriage.

High Thyroxine Hormone Level

When a person has high levels of thyroxine in the body, then he may become a candidate of hyperthyroidism. When a person has hyperthyroidism, he may be at risk for developing Grave’s disease, chronic thyroiditis, trophoblastic disease and toxic multimodal goiter. Common symptoms of hyperthyroidism are as follows

  • Hyperactivity
  • Insomnina
  • Heat sensitivity
  • Excessive Sweating
  • Tremors
  • Lid protrusion
  • Irregular and rapid heart beat

Along with these symptoms, persons with hyperthyroidism are prone to Plummer’s nail disease and may be at risk for heart failure if treatment is not given as soon as possible.

Thyroxine as a Pharmacological Treatment 

Persons who have low thyroxine level or hypothyroidism are often prescribed with synthetic medications called thyroxine or levothyroxine.

Popular brands include Synthroid and Levothroid. Some medications, such as Armour Thyroid are taken from desiccated thyroid glands of bovine or porcine animals.

These medications supplement the lack of thyroxine in the body by providing synthetic hormones that are identical to thyroxine itself.

While these medications are generally effective – they may cause side effects. The common side effects that you should watch out for when taking synthetic thyroxine drugs are as follows:

  • Hyperactivity
  • Insomnia
  • Headache
  • Fatigue
  • Excessive sweating
  • Anxiety
  • Appetite changes
  • Weakness

These side effects are usually experienced when one takes more than the recommended dosage, so if you start to experience side effects like these, you may need to have your dosage modified.

Synthethic versus Natural

The only difference between natural thyroxine from synthetic thyroxine is that natural thyroxine is made by the body. The production of natural thyroxine is controlled by the feedback system involving the hypothalamus, the thyroid glands and pituitary glands. These parts of the body work in conjunction to be able to maintain and produce the normal hormonal level that the body needs.

When one of these parts goes haywire – the production of the thyroid hormones is affected. This causes the thyroid hormone levels to either drop or increase. What is great though, is that there are supplements that actually help the functioning of these important glands and body parts. Thyax is just one type of product that helps with this.

The only time that synthetic thyroxine is given is when the person does not produce enough thyroxine or can no longer produce thyroxine naturally. Synthetic thyroxine aids in maintaining thyroid hormone balance, which helps stop the symptoms of hypothyroidism and promotes proper health and wellness.  

Next Article: Thyroid Health | How to Boost T3 and T4 Levels