Hypothyroidism is a condition in which the thyroid gland does not produce enough thyroid hormones to meet the body's needs.
Hypothyroidism occurs when the body has insufficient thyroid hormone. Hashimoto's disease is a common cause in iodine-sufficient regions. Other causes include thyroid surgery, radioactive iodine treatment, certain medicines and disorders affecting the pituitary or hypothalamus.
The thyroid is a butterfly-shaped endocrine gland located at the front of the neck. It produces mainly thyroxine (T4) and triiodothyronine (T3), which influence metabolism and many organ systems.
Hypothyroidism can begin when the thyroid gland is damaged or unable to produce adequate hormone, or when the pituitary or hypothalamus fails to provide appropriate stimulation.
The thyroid normally produces hormones that help regulate metabolism and many body functions. In hypothyroidism, insufficient thyroid hormone slows these processes. In primary hypothyroidism, the thyroid gland itself is usually affected and the pituitary gland typically increases TSH production.
Hypothyroidism may be classified as primary thyroid failure, central hypothyroidism caused by pituitary or hypothalamic disease, congenital hypothyroidism, overt hypothyroidism or subclinical hypothyroidism.
Important types include primary hypothyroidism, commonly caused by Hashimoto's disease; central hypothyroidism from pituitary or hypothalamic disorders; congenital hypothyroidism; and subclinical hypothyroidism, in which TSH is elevated while free T4 remains within the reference range.
Fatigue or unusual tiredness
Increased sensitivity to cold
Weight gain
Constipation
Dry skin
Hair thinning or hair changes
Muscle aches or weakness
Low mood or depression
Difficulty concentrating or slowed thinking
Heavy or irregular menstrual periods
Causes include Hashimoto's autoimmune thyroiditis, thyroid surgery, radioactive iodine treatment, certain medicines, iodine deficiency or excess, thyroiditis and disorders affecting the pituitary or hypothalamus.
Female sex
Increasing age
Family history of thyroid disease
Personal history of autoimmune disease
Previous thyroid surgery or radioactive iodine treatment
Certain medicines
Pregnancy or recent pregnancy
Diagnosis uses thyroid function tests, usually beginning with TSH and followed by free T4 when appropriate. Thyroid antibodies may help identify autoimmune thyroid disease such as Hashimoto's disease.
Dry or coarse skin
Slow heart rate
Thyroid enlargement or goiter
Delayed relaxation of deep tendon reflexes
Puffiness around the eyes or face
Cold extremities or cold intolerance
Changes in weight
Slowed speech or movements
TSH
Free T4
Thyroid peroxidase antibodies
Thyroglobulin antibodies when clinically useful
Complete blood count when indicated
Lipid profile
Electrolytes and other targeted tests when clinically indicated
Thyroid ultrasound when a thyroid nodule, goiter or structural abnormality requires assessment
Pituitary MRI when central hypothyroidism or pituitary disease is suspected
Other thyroid imaging only when clinically indicated
Repeat thyroid-function testing
Assessment for thyroid autoantibodies
Pituitary hormone evaluation when central hypothyroidism is suspected
Assessment for associated autoimmune disease when clinically indicated
Pregnancy-specific thyroid-function assessment when appropriate
Iron deficiency anemia
Depression
Sleep disorders
Vitamin deficiencies
Chronic kidney or liver disease
Medication-related fatigue
Other endocrine disorders
Hypothyroidism is not usually staged like cancer. Clinicians classify it according to cause and laboratory findings, including overt hypothyroidism, subclinical hypothyroidism and central hypothyroidism.
Staging or grading systems differ between diseases. The information here is educational and should be interpreted by a qualified healthcare professional in the context of the individual case.
The standard treatment for most persistent primary hypothyroidism is levothyroxine, a synthetic form of T4. The dose is individualized and monitored using thyroid-function tests. Treatment of the underlying cause and associated conditions may also be required.
Levothyroxine for persistent hypothyroidism
Dose adjustment of levothyroxine based on clinical assessment and thyroid-function testing
Treatment of the underlying cause or associated condition when appropriate
Avoid routine use of thyroid hormone supplements or combination therapy without specialist assessment
Medicines listed here are for educational information only. Do not start, stop, or change a medicine without professional medical advice.
Untreated or inadequately treated hypothyroidism can contribute to high cholesterol, cardiovascular problems, infertility or menstrual problems, pregnancy complications and, rarely, severe myxedema coma.
Extreme drowsiness, confusion or difficulty staying awake
Very low body temperature
Markedly slow breathing
Severe weakness with reduced responsiveness
Loss of consciousness
Severe deterioration in a person with known untreated hypothyroidism
If symptoms are severe, rapidly worsening, or life-threatening, seek emergency medical care immediately.
With appropriate diagnosis and treatment, most people can maintain normal thyroid hormone levels and live normally. Untreated severe hypothyroidism can rarely progress to life-threatening myxedema coma.
Survival statistics describe outcomes in groups of people and cannot predict exactly what will happen to one individual. Prognosis depends on factors such as cancer stage, tumor biology, treatment response, overall health, and follow-up.
Hypothyroidism occurs worldwide and is more common in women and older adults. Autoimmune thyroid disease is a major cause in iodine-sufficient populations.
Adequate iodine nutrition, appropriate management of thyroid disease and avoidance of unnecessary high-dose iodine or thyroid supplements can reduce some preventable thyroid problems.
What is causing my hypothyroidism?
What are my TSH and free T4 results?
Do I need thyroid antibody testing?
What levothyroxine dose is appropriate for me?
When should my thyroid blood tests be repeated?
How should I take levothyroxine in relation to food and other medicines?
Could another condition be causing my symptoms?
Do I need special thyroid monitoring during pregnancy?
BimariDur provides educational health information to help people understand diseases, symptoms, tests, and treatment concepts. It does not replace examination, diagnosis, or treatment by a qualified healthcare professional.
Do not delay professional medical care because of information read on BimariDur.