What is hypothyroidism and how is it treated?

Understanding Hypothyroidism

What Is Hypothyroidism?

Hypothyroidism is a condition where your thyroid gland—a small butterfly-shaped gland in your neck—doesn't produce enough thyroid hormones to keep your body running normally. 1, 2

Think of thyroid hormones as your body's "gas pedal" that controls how fast or slow your metabolism runs. When you don't have enough of these hormones, everything in your body slows down 1, 3.

Common Symptoms You Might Experience

• Feeling exhausted all the time - This affects 68-83% of people with hypothyroidism, making it the most common complaint 2
• Unexplained weight gain - Occurs in 24-59% of patients because your body burns calories more slowly 2
• Always feeling cold - Your body produces less heat when metabolism slows down 1, 4
• Constipation - Your digestive system slows down along with everything else 4, 5
• Dry, rough skin - Reduced metabolism affects skin cell turnover 4, 5
• Memory problems and difficulty concentrating - Affects 45-48% of patients 2
• Voice changes or hoarseness 4
• Irregular menstrual periods - Occurs in approximately 23% of women with hypothyroidism 2

What Causes It?

In developed countries with adequate iodine in the diet, the most common cause is Hashimoto's thyroiditis—an autoimmune disease where your immune system mistakenly attacks your thyroid gland. 6, 7, 2 This accounts for up to 85% of cases 7, 2.

Other causes include 6, 7:

• Previous thyroid surgery - Removal of part or all of the thyroid gland
• Radioactive iodine treatment - Used to treat overactive thyroid
• Radiation therapy to the neck - For cancer treatment
• Certain medications - Including amiodarone and immune checkpoint inhibitors
• Iodine deficiency - The leading cause worldwide, though rare in developed countries 7, 3

Who Gets Hypothyroidism?

• Women are affected much more often than men 3, 2
• Older adults have higher rates - The condition becomes more common with age 3, 2
• People with type 1 diabetes - Have increased risk 2
• Those with a family history - Having a first-degree relative with hypothyroidism increases your risk 2

How Is It Diagnosed?

Your doctor diagnoses hypothyroidism with a simple blood test that measures thyroid-stimulating hormone (TSH) and free thyroxine (T4). 7, 4, 2

• High TSH with low free T4 = You have hypothyroidism 2
• High TSH with normal free T4 = You have subclinical (mild) hypothyroidism 8

Population-wide screening is not recommended for people without symptoms. 7, 4 Testing should be done when you have symptoms or risk factors 7.

How Is It Treated?

The treatment is straightforward: you take a daily pill called levothyroxine, which is synthetic thyroid hormone that replaces what your body isn't making. 9, 3, 4, 2

Starting Treatment

• For most adults under 60 without heart disease: Start with 1.6 micrograms per kilogram of body weight per day 8, 3, 4
• For people over 60 or with heart disease: Start with a much lower dose (12.5-50 micrograms per day) and increase slowly to avoid stressing the heart 8, 4, 2

Monitoring Your Treatment

• Your doctor will recheck your blood tests 6-8 weeks after starting medication or changing your dose 8, 4
• Once your levels are stable, you'll need blood tests every 6-12 months 8
• The goal is to get your TSH level into the normal range (0.4-4.5 mIU/L) 3

Important Treatment Details

• Take levothyroxine on an empty stomach, 30-60 minutes before breakfast - Food interferes with absorption 9
• This is usually lifelong treatment - Most people need to take it for the rest of their lives 3, 4
• Don't stop taking it even if you feel better - Your symptoms improve because the medication is working 4
• If you're pregnant, your dose will need to increase by about 30% - Tell your doctor immediately if you become pregnant 8, 9, 4

Common Pitfalls to Avoid

• About 25% of patients end up on doses that are too high, which can cause heart problems and bone loss 8
• Taking your medication inconsistently - This is the most common reason treatment doesn't work well 6
• Not waiting long enough between dose changes - It takes 6-8 weeks for your body to reach a new steady state 8

What Happens If It's Not Treated?

Untreated hypothyroidism can lead to serious complications: 2, 5

• Heart failure - Your heart has to work harder when metabolism is too slow 2
• Infertility and miscarriage risk - Thyroid hormones are essential for reproduction 2
• In infants: mental retardation and delayed development - This is why newborns are screened 1
• Myxedema coma - A rare but life-threatening emergency with a 30% mortality rate, characterized by severe hypothermia, low blood pressure, and altered mental status 4, 2

Living With Hypothyroidism

With proper treatment, most people with hypothyroidism can lead completely normal, healthy lives. 1, 5

• Your symptoms should improve within a few weeks of starting treatment 4
• Weight management and regular exercise can help with persistent symptoms 1
• You'll need regular follow-up with your doctor to ensure your medication dose remains appropriate 8, 4
• Some medications and supplements can interfere with levothyroxine absorption, so always tell your doctor about everything you're taking 6