Hypothyroidism drugs
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Hypothyroidism Drugs: An Overview
Introduction to Hypothyroidism and Its Treatment
Hypothyroidism, a condition characterized by an underactive thyroid gland, affects up to 5% of the general population, with an additional 5% potentially undiagnosed7. The most common cause in iodine-sufficient areas is Hashimoto's disease, an autoimmune disorder7. The primary treatment for hypothyroidism is hormone replacement therapy, typically with levothyroxine (LT4), a synthetic form of thyroxine (T4)5 7.
Levothyroxine: The Standard Treatment
Levothyroxine is the most widely prescribed medication for hypothyroidism and is considered the drug of choice5. It is usually administered at a starting dose of 1.6 µg/kg/day, which is then adjusted to maintain optimal thyroid-stimulating hormone (TSH) levels7. Levothyroxine effectively reverses the symptoms of hypothyroidism in most patients, although some may continue to experience symptoms despite treatment3 7.
Combination Therapy: Levothyroxine and Liothyronine
For patients who remain symptomatic on levothyroxine alone, combination therapy with levothyroxine and liothyronine (LT3) has been explored. Liothyronine is a synthetic form of triiodothyronine (T3), the more active thyroid hormone at the cellular level4. Clinical trials have shown mixed results, with some studies indicating improved mood, quality of life, and cognitive function with combination therapy4 9. However, the potential for adverse effects and the lack of clear advantages over levothyroxine monotherapy mean that levothyroxine alone remains the standard treatment4 9.
Drug-Induced Hypothyroidism
Various drugs can induce hypothyroidism by different mechanisms. Some drugs inhibit the synthesis or release of thyroid hormones, while others induce thyroiditis or interfere with thyroid hormone absorption and metabolism2. Medications such as amiodarone, lithium, and interferon are known to affect thyroid function and should be monitored closely2. Additionally, drugs like glucocorticoids and dopamine agonists can suppress TSH, potentially leading to central hypothyroidism1 2.
Pharmacokinetics and Drug Interactions
Thyroid dysfunction can significantly alter the pharmacokinetics of various drugs. For instance, hypothyroidism can prolong the half-life of certain medications, necessitating dose adjustments6. Conversely, hyperthyroidism can accelerate drug metabolism, requiring higher doses6. Understanding these interactions is crucial for managing patients with thyroid disorders effectively.
Special Considerations in the Elderly
Hypothyroidism is particularly common among the elderly, and levothyroxine is one of the most frequently prescribed medications in this population10. In older adults, the diagnosis and treatment of hypothyroidism must be carefully tailored, considering factors such as age-related changes in TSH levels, comorbidities, and the risk of overtreatment10. Personalized therapy is essential to avoid potential adverse effects and ensure optimal patient outcomes10.
Conclusion
Hypothyroidism is a prevalent condition that can be effectively managed with hormone replacement therapy, primarily levothyroxine. While combination therapy with liothyronine may benefit some patients, it is not universally recommended due to the potential for adverse effects. Drug-induced hypothyroidism and altered pharmacokinetics in thyroid dysfunction highlight the need for careful monitoring and individualized treatment plans, especially in the elderly. Further research is needed to optimize treatment strategies and improve the quality of life for all patients with hypothyroidism.
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Drugs that suppress TSH or cause central hypothyroidism.
Drugs like glucocorticoids, dopamine agonists, and somatostatin analogues can suppress thyroid hormone levels, but most do not cause central hypothyroidism.
Highly CitedDrug-induced hypothyroidism.
The thyroid axis is particularly prone to interactions with a wide variety of drugs, whose list increases year by year. Hypothyroidism is the most frequent consequence of drug-induced thyroid dysfunction. The main mechanisms involved in the development of primary hypothyroidism are: inhibition of the synthesis and/or release of thyroid hormones, immune mechanisms related to the use of interferon and other cytokines, and the induction of thyroiditis associated with the use of tyrosine kinase inhibitors and drugs blocking the receptors for vascular endothelial growth factor. Central hypothyroidism may be induced by inhibition of thyroid-stimulating hormone (bexarotene or corticosteroids) or by immunological mechanisms (anti-CTLA4 or anti-PD-1 antibody drugs). It is also important to recognize those drugs that generate hypothyroidism by interaction in its treatment, either by reducing the absorption or by altering the transport and metabolism of levothyroxine. Thus, it is strongly recommended to evaluate thyroid function prior to the prescription of medications such as amiodarone, lithium, or interferon, and the new biological therapies that show important interaction with thyroid and endocrine function in general.
Rigorous JournalRisks and safety of combination therapy for hypothyroidism
Combination therapy with levothyroxine and liothyronine may improve patient satisfaction with monotherapy, but new trials are needed to avoid non-physiologic hormone ratios, inadvertent thyrotoxicosis, and unacceptable side effects.
Systematic ReviewTreatment of hypothyroidism with levothyroxine or a combination of levothyroxine plus L-triiodothyronine.
Levothyroxine alone remains the treatment of choice for hypothyroidism, while combined levothyroxine plus liothyronine may have beneficial effects on mood, quality of life, and psychometric performance.
Drugs for hypothyroidism.
Levothyroxine is the preferred drug for treating hypothyroidism, which is often caused by Hashimoto's thyroiditis, thyroidectomy, or radioactive iodine therapy.
Influence of Thyroid Dysfunction on Drug Pharmacokinetics
Thyroid dysfunction alters drug absorption, metabolism, and excretion, affecting drug pharmacokinetics in both hypothyroidism and hyperthyroidism.
Highly CitedHypothyroidism in Context: Where We’ve Been and Where We’re Going
Levothyroxine is the main tool for treating hypothyroidism, but optimal treatment requires further research on accurate prevalence assessments, optimal substitution doses, and optimal duration of treatment.
Highly CitedThyroid hormone replacement for central hypothyroidism: a randomized controlled trial comparing two doses of thyroxine (T4) with a combination of T4 and triiodothyronine.
A dose of 1.6 microg/kg bw of thyroxine (T4) based on body weight improves markers associated with central hypothyroidism, suggesting that T4 dosage based on body weight is superior to titration aiming at middle normal fT4 concentrations.
RCTHighly CitedLIOTHYRONINE AND DESICCATED THYROID EXTRACT IN THE TREATMENT OF HYPOTHYROIDISM.
Combination therapy with LT4+LT3 can effectively restore euthyroidism and normalize serum TSH in hypothyroid patients without increased risk of cardiovascular disease, AF, or fractures.
Observational StudyRigorous JournalHypothyroidism in the Elderly: Who Should Be Treated and How?
Personalized therapy is crucial for managing hypothyroidism in the elderly, considering age-dependent TSH cutoffs, thyroid autoimmunity, comorbidities, and frailty.
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