What Happens If TSH Levels Are High or Low?

Medically Reviewed on 12/9/2022

What happens when TSH level is high?

An elevation in the thyroid-stimulating hormone (TSH) level indicates that the thyroid gland
An elevation in the thyroid-stimulating hormone (TSH) level indicates that the thyroid gland is not functioning properly

An elevation in the thyroid-stimulating hormone (TSH) level indicates that the thyroid gland is not functioning properly. The TSH hormone controls the level of T3 and T4 hormones in the body, which in turn carry out various cell functions.

A high TSH level is often found in conditions that cause T3 and T4 levels to drop, causing the brain (pituitary gland) to compensate by increasing the serum TSH levels. This condition is called hypothyroidism.

What causes TSH level to rise?

  • Hashimoto's thyroiditis: This is a condition in which your body begins to attack its thyroid gland through an autoimmune process, which results in long-term and potentially permanent damage to the thyroid gland over time.
  • Iodine deficiency: Iodine is required for the production of the thyroid hormone in your body. Low iodine content in your diet will result in low circulating thyroid hormone in the serum. This may trigger a feedback loop that results in an increase in the TSH level from your pituitary.
  • Obesity and metabolic damage: Obesity, weight gain, and metabolic damage can all potentially increase your TSH levels and lead to hypothyroidism. Women with polycystic ovarian disease are especially at risk.
  • Stress and increased cortisol: A high TSH level may also be due to stress and increased cortisol levels. A high cortisol level is positively correlated with TSH levels in the serum. Cortisol is the stress hormone and is released in response to stressful situations.
  • Thyroidectomy (partial or complete): Damage to or removal of your thyroid gland may increase TSH levels.
  • Drugs: Lithium, metformin, and other drugs are known to cause thyroid dysfunction.

The normal range of TSH levels in non-pregnant adult women is 0.5 to 5.0 mIU/L. A TSH level higher than 5.0 usually indicates an underactive thyroid (hypothyroidism) and a TSH level lower than 0.4 indicates the presence of excessive thyroid hormone and overactive thyroid (hyperthyroidism). Abnormal TSH and thyroid hormone levels commonly indicate the following conditions:

Abnormal Thyroid (TSH) Levels and Possible Conditions Chart
Possible Conditions Lab Results
Primary hypothyroidism High TSH, low thyroid hormones
Subclinical hypothyroidism High TSH, normal thyroid hormones
Primary hyperthyroidism Low TSH, high thyroid hormones
Subclinical hyperthyroidism Low TSH, normal thyroid hormones

Low TSH, high thyroid hormone followed by

high TSH, low thyroid hormone

Pituitary disease Low TSH, low thyroid hormones
Early or mild hyperthyroidism Low TSH, normal thyroid hormone level

Symptoms and treatment of high TSH levels

Symptoms of high TSH levels

The standard reference range for the TSH level is anywhere between 0.30 and 5.0 uIU/mL. If your TSH level is higher than 5.0 uIU/mL, then the lab will flag you as “high,” and you may experience the symptoms listed above 5.0 uIU/mL. Values of a TSH level of more than 10.0 uIU/mL need long-term thyroid supplements.

Subclinical hypothyroidism is seen where TSH levels are between 5.0 and 10.0 uIU/mL but T4 levels are normal. This may need to be treated with supplements if it causes symptoms or if the woman is at present pregnant. Often subclinical hypothyroidism settles on its own with lifestyle changes, diet, and stress management.

Treatment for high TSH levels

  • Using thyroid hormone T4 supplements will help reduce your TSH level due to the feedback loop that exists in your body.
  • Treating the underlying cause. For example, iodine deficiency can be reversed if treated appropriately by adding sufficient iodine to your daily diet.
  • In cases of stress, you may be able to improve your TSH level by reducing stress and lowering your cortisol levels through yoga and other relaxing activities.
  • The use of supplements that contain both zinc and selenium may improve thyroid function in those with deficiencies in these minerals.


Hyperthyroidism: Symptoms, Treatment, Medication See Slideshow

What happens if TSH level is low?

Having low TSH levels means that your thyroid gland is producing thyroid hormones in excess, which is called hyperthyroidism. In this condition, the pituitary gland decreases the amount of TSH it secretes to offset the high amount of thyroid hormones (namely, thyroxine and triiodothyronine) in your body. 

Causes of low TSH levels

  • Too much thyroid hormone production (endogenous hyperthyroidism): The most common cause of overactive thyroid is a condition called Graves’ disease, which is hereditary (passed down in families). Graves’ disease is an autoimmune disease in which the body's immune system causes the thyroid gland to produce too much thyroid hormone.
  • Too much or overdosage of thyroid medication (exogenous hyperthyroidism).
  • Not enough production of TSH from the pituitary gland.
  • Benign (non-cancer) tumors of the thyroid (called thyroid nodules) or pituitary gland.
  • Too much iodine in the body can be caused by taking iodine supplements such as kelp or seaweed.
  • Inflammation of the thyroid gland may be caused by a virus or a problem with the immune system.
  • Some medications, such as lithium or amiodarone, can cause an overactive thyroid.

Symptoms and treatment of low TSH levels

Symptoms of low TSH levels

Treatment of low TSH levels

Treatment depends on the patient’s age, the type of overactive thyroid that they have, the severity of the condition, and other medical conditions that may be affecting the patient’s health.

Possible treatments for overactive thyroid include:

  • Medications:
    • Beta-blockers such as propranolol or metoprolol: Relieve symptoms such as shaking or tremors and fast heartbeat. These medicines are given for a short time and can help alleviate symptoms while treatment is being decided.
    • Antithyroid medications such as carbimazole: Helps to reduce the amount of thyroid hormone that is produced by the glands. 
  • Radioactive iodine therapy:
    • Involves taking a drink or swallowing a capsule, which contains radioactive iodine.
    • Damages the cells that produce the thyroid hormones in the thyroid gland.
  • Surgery:
    • Involves a procedure in which all or part of the thyroid gland is removed.
    • Often the last resort is considered if all other therapies and medication have not worked. People often consider surgery if they are at a higher risk of experiencing side effects from other treatments.
    • Surgery is a good option if the patient has a goiter that causes problems in the neck.

What are signs of high TSH levels in newborns?

The high TSH level can indicate your newborn may have congenital hypothyroidism.  If it is not treated within 2 weeks, it can lead to the following symptoms in babies:

  • Uninterested in taking breast or bottled milk: They may fall asleep while feeding because it becomes hard for them to stay awake.
  • Often quiet and seldom cry: They may sleep for hours and need to be awakened for feeding. They may not respond to stimulation or cry as much as other babies.
  • Poor growth and poor weight gain: At birth, babies with high TSH levels are as large as newborn infants, but gradually, they may start to lose weight.
  • Slow heart rate and low blood pressure: Their hands and feet may be cold to the touch due to poor blood circulation.
  • Jaundice: They may have yellowing of the skin that persists for quite some time. Their skin may also appear pale and blotchy.

Hypothyroidism can cause brain development delays, teething delays, milestone delays (due to weak muscles), and low intellectual ability. Timely intervention is therefore key.

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What are 7 causes of high TSH levels in newborns?

What Causes High TSH Levels in Newborns
Congenital hypothyroidism is the most common cause of high levels of thyroid-stimulating hormone (TSH) in newborns. Learn about other causes

Congenital hypothyroidism is the most common cause of high levels of thyroid-stimulating hormone (TSH) in newborns. 

If left untreated, congenital hypothyroidism can lead to prolonged neonatal jaundice, developmental delays, and mental retardation.

7 causes of high TSH levels in newborns

  1. Congenital hypothyroidism: Congenital hypothyroidism occurs when the thyroid gland fails to develop or function properly. In 80%-85% of cases, the thyroid gland is absent, severely reduced in size (hypoplastic), or abnormally located. Causes of congenital hypothyroidism may be the use of carbimazole, methimazole, and other antithyroid medications by the mother during pregnancy.
  2. Transient hypothyroidism: Transient hypothyroidism refers to a temporary deficiency of the thyroid hormone after birth (low T4 and elevated TSH levels), which corrects itself a few months after birth, during infancy.
  3. Congenital syndromes: Babies born with Pendred syndrome, Bamforth-Lazarus syndrome, and brain-lung-thyroid syndrome have hypothyroidism as part of the disease.
  4. Premature birth: In one study, babies born prematurely had the highest TSH levels, and those with severe illness were at the highest risk of abnormally elevated TSH levels. Diseases that may result in higher TSH levels include:
    1. Respiratory distress syndrome
    2. Persistent ductus arteriosus (heart defect caused by problems in the development of the heart)
    3. Necrotizing enterocolitis (severe gastrointestinal problems)
  5. Maternal thyroid disorders or maternal medications: Thyroid disease in the mother can cause thyroid suppression in her children. Untreated Graves’ disease in the mother is one of the major causes of high TSH levels in newborns. Certain medications taken by the mother during pregnancy can also elevate TSH levels in babies.
  6. Iodine deficiency: Iodine deficiency in the diet is a major cause of congenital or transient hypothyroidism in newborns in many developing countries.
  7. Errors: Errors in the thyroid screening procedure or incorrect normal result intervals for that particular age are less common causes of high TSH levels in newborns.

What are the complications of hypothyroidism if left untreated?

If hypothyroidism is left untreated or not treated properly, a life-threatening complication called myxedema can occur. Myxedema is considered a medical emergency that can also be triggered by a trauma, an infection, surgery, uncontrolled diabetes, pregnancy or labor, or going off thyroid medications.

Symptoms may include:

Medically Reviewed on 12/9/2022
Image Source: iStock Images

Hypothyroidism: https://my.clevelandclinic.org/health/diseases/12120-hypothyroidism