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Hypothyroidism Treatment

Hypothyroidism treatment is best accomplished using levothyroxine,1

a synthetic form of the thyroid hormone T4.2

Occasionally, hypothyroidism treatment is done with a combination of thyroxine or tetraiodothyronine (T4) and triiodothyronine (T3), but knowing which patients will benefit from this combination treatment is not well understood. It should be avoided in women who are pregnant or planning a pregnancy.3

Desiccated (dried) pig thyroid is also available for hypothyroidism treatment – and until the 1960s was the only hypothyroidism treatment option.4 It is prescribed only on rare occasion nowadays.5

Patients with obvious hypothyroidism [Thyroid stimulating hormone (TSH) levels*6 greater than 10 mIU/L] should be treated. Alternatively, patients with subclinical hypothyroidism†7 may not require treatment with levothyroxine.7 Whether or not you need levothyroxine treatment depends on a number of factors, such as:

  • The severity of your symptoms8
  • The presence or absence of anti-thyroid antibodies in your system8

About Levothyroxine

The daily dosage of levothyroxine is dependent on age, sex (male or female), and weight.5,9

Other factors can affect how much levothyroxine you need, such as certain health conditions and other medications.5

Levothyroxine has a small therapeutic window, which means that the dose has to be tailored to the individual10 to avoid the consequences of over- or under-treatment.11

Levothyroxine has few side effects2 and is usually well tolerated.5

It takes several weeks for levothyroxine to build up in the body and for TSH levels to stabilize; symptoms may also take several weeks to resolve.2

At the start of treatment, it’s important to have TSH levels checked regularly (after 8 weeks7 or more often if required by your doctor) to make sure that the dose is correct and thyroid function has returned to normal.5

After TSH levels are stabilized, a TSH test should generally be done after 6 months and then every year7 or more often if required by your doctor, because factors like health, weight, and age can affect dosing.5

Staying on the same brand of levothyroxine

When it comes to hyperthyroidism medication, experts recommend that patients stay on the same levothyroxine preparation throughout treatment, which is usually for the remainder of their lives12

This is because different brands may be absorbed differently by your intestines, even at the same dose.12

Because levothyroxine has a small therapeutic window,10 these differences in absorption could lead to over- or under-treatment that have unwanted consequences.11

If a brand switch occurs, it is recommended that patients have their TSH levels checked, as they may need to have their hypothyroidism medication dose adjusted until their TSH levels have stabilized.12

Risks of over- or under-treatment

Because levothyroxine has a small therapeutic window,10 finding the correct dose is important to avoid the consequences of over- or under-treatment.11 Essentially, overtreatment will result in hyperthyroidism, whereas under-treatment will not resolve the symptoms of hypothyroidism.6

Either way, the wrong dose can have an effect on:

  • Growth and development13
  • Heart function2
  • Bone health14
  • Reproduction13
  • Ability to think13
  • Emotional state (your mood)13
  • stomach cramps13
  • Metabolism of sugar and fats15

If your dose of levothyroxine is too high, you may experience symptoms of hyperthyroidism. These can include:

  • Chest pain or a fast or irregular heartbeat14
  • Irritability14
  • Nervousness and sweating14
  • Increased appetite13
  • Diarrhea14
  • Sleeplessness14

If you are experiencing these symptoms, contact your doctor. He or she may order a TSH test to determine if your TSH levels are too low. If this is the case, your dose of levothyroxine will likely be lowered.

*Normal TSH levels range from 0.5 to 5.5 mIU/L.

†Subclinical hypothyroidism (SCH) is also called mild thyroid failure with elevated thyroid-stimulating hormone (TSH) levels and normal thyroid hormone levels.

References:

1. Jonklaas J, Bianco AC, Bauer AJ, et al. Guidelines for the treatment of hypothyroidism: prepared by the American Thyroid Association Task Force on Thyroid Hormone Replacement. Thyroid. 2014;24(12):1670-1751. 2. Levothyroxine. National Health Service. Accessed May 12, 2023. https://www.nhs.uk/medicines/levothyroxine/ 3. Wiersinga WM, Duntas L, Fadeyev V, Nygaard B, Vanderpump MP. 2012 ETA guidelines: the use of L-T4 + L-T3 in the treatment of hypothyroidism. Eur Thyroid J. 2012;1(2):55-71. 4. Biondi B, Wartofsky L. Treatment with thyroid hormone. Endocrine Rev. 2014;35(3):433-512. 5. Thyroid hormone treatment. American Thyroid Association. Accessed May 12, 2023. https://www.thyroid.org/wp-content/uploads/patients/brochures/HormoneTreatment_brochure.pdf 6. Miragaya J. Hypothyroidism: overtreatment and under treatment of hypothyroidism with thyroid hormone is associated with increased death from heart disease. Clinical Thyroidology for the Public. 2023;16(2):3-4. 7. Fatourechi V. Subclinical hypothyroidism: an update for primary care physicians. Mayo Clin Proc. 2009;84(1):65-71. 8. Hypothyroidism. MedlinePlus. Accessed May 12, 2023. https://medlineplus.gov/hypothyroidism. html 9. Younis IR, Ahmed MA, Burman KD, Soldin OP, Jonklaas J. Stable isotope pharmacokinetic studies provide insight into effects of age, sex, and weight on levothyroxine metabolism. Thyroid. 2018;28(1):41-49. 10. Brun VH, Eriksen AH, Selseth R, et al. Patient-tailored levothyroxine dosage with pharmacokinetic / pharmacodynamic modeling: a novel approach after total thyroidectomy. Thyroid. 2021;31(9):1297-1304. 11. Duntas LH, Jonklaas J. Levothyroxine dose adjustment to optimise therapy throughout a patient’s lifetime. Adv Ther. 2019;36(suppl 2):30-46. 12. Benvenga, S, Carlé A. Levothyroxine formulations: pharmacological and clinical implications of generic substitution. Adv Ther. 2019;36(suppl 2):59-71. 13. Levothyroxine (oral route). Mayo Clinic. Accessed May 15, 2023. https://www.mayoclinic.org/drugs-supplements/levothyroxine-oral-route/side-effects/drg-20072133 14. Levothyroxine. MedlinePlus. Accessed May 15, 2023. https://medlineplus.gov/druginfo/meds/a682461.html 15. Levothyroxine. Drug Bank Online. Accessed August 10, 2023. https://go.drugbank.com/drugs/DB00451