Hypothyroidism

What is Hypothyroidism?

Hypothyroidism occurs when the thyroid gland does not produce enough thyroid hormone to satisfy the body’s needs. This is also known as an ‘underactive thyroid’.

The thyroid is a butterfly-shaped gland located in the front of the neck which produces thyroid hormone. This hormone affects almost every organ in the body. Primarily the thyroid controls the body’s metabolism. Without the thyroid working properly, the body’s natural metabolism becomes unbalanced leading to either too little thyroid hormone, hypothyroidism or too much thyroid hormone, hyperthyroidism.

Hypothyroidism will lead to many of the body’s essential functions to slow, while hyperthyroidism will speed the functions up.

There are a number of thyroid diseases, but hypothyroidism is the most common type of thyroid function problem. It affects 1 in 33 Australians according to Hormones Australia, affecting slightly more women than men, typically more often in those aged over 60.

Hypothyroidism Symptoms

As thyroid hormone affects so many parts of the body, there can be many signs and symptoms of a thyroid problem. These symptoms can vary in severity based on how severe the deficiency in thyroid hormone is. Development of the condition is often gradual, making symptoms of hypothyroidism hard to recognise at first.

The first symptoms of those developing hypothyroidism are often weight gain and fatigue. Unexplained weight gain without diet or exercise changes comes as a result of a slowed metabolism.

Other symptoms that may indicate low thyroid hormone levels are:

• Slow heart rate
• Depression
• Constipation
• Sensitivity to the cold
• Thinning hair
• Joint and muscle tenderness
• Dry skin
• Fertility problems
• Menstrual changes
• Sexual dysfunction and decreased libido

In its most severe form, hypothyroidism can be life-threatening causing a severe slowing of the body’s essential functions. This typically will only occur if the condition is left untreated for an extended period of time.

Causes

A number of situations and other conditions can lead to hypothyroidism. Common causes of hypothyroidism include:

• Some medications - such as lithium and amiodarone
• Hashimoto’s disease - an immune system dysfunction
• Congenital hypothyroidism
• Radiation therapy
• Pituitary gland dysfunction
• Thyroid removal (part or whole) - usually due to thyroid cancer
• Overtreatment with hyperthyroidism treatments
• Iodine deficiency

Diagnosis

To confirm a diagnosis of hypothyroidism, a blood test needs to happen. This looks for thyroid-stimulating hormone (TSH) levels from the pituitary gland. As a result of low thyroid hormone, the pituitary gland will release large amounts of TSH detectable in the blood.

Typically doctors will also look for T4 levels, a hormone produced by the thyroid. Low T4 together with high TSH levels usually indicate whether you have hypothyroidism. 

Thyroid functions tests (TFT) are able to gauge how severe the condition is, allowing the doctor to adjust the treatment dose accordingly.

Hypothyroidism Treatments

To treat hypothyroidism, medicines are used to replace the missing thyroid hormone, ideally bringing them back to a regular and stable level. Treatment of hypothyroidism is typically lifelong after diagnosis, with only a few exceptions (treating iodine deficiency). The dose you require may change over time and as such monitoring of the condition with blood tests is required periodically.

Thyroid Hormone

Thyroid hormone replacement tablets come in a variety of strengths. Everyone’s dose may slightly differ as the hormone required for the body and thyroid function may differ from others. The medicine comes in two major forms, refrigerated or shelf-stable. While both contain thyroid hormone, the doses are not interchangeable so it is important that you do not change form or dose without consulting a doctor.

Both treatments should be taken on an empty stomach to ensure absorption. Both have similar side effects, mostly relating to if the body is receiving too much or too little hormone. Once stable, side effects should be minimal. If you are experiencing side effects, you should consult your doctor and have a thyroid function test.

Monitoring

The dose you need may change over time as your body ages and changes. Getting your dose right is a balancing act. Too little medicine, hypothyroidism remains, too much and you could experience hyperthyroidism. 

Regular monitoring and blood tests with a doctor are important to find a dose that’s right for you and ensure it remains the right dose. Thyroid hormone levels can take weeks to months to stabilise after treatment. Generally, blood tests are completed 6-8  weeks after starting. Once a stable dose is achieved blood tests are only required every 6-12 months.

Written by Clinical Pharmacist Tyson Wilkman