Prescription thyroid products that contain both T4 and T3 are known as desiccated thyroid products, which contain ground up and dried thyroid glands, mostly from pigs. Desiccated thyroid products include:
- Armour Thyroid
- NP Thyroid
- WP Thyroid
Desiccated thyroid products are generally not recommended for the treatment of hypothyroidism by most guidelines due to the fact that there may be inconsistency in potency between products and there is far more data supporting the use of levothyroxine. However, there are cases where desiccated thyroid may be preferred, such as in individuals that don't efficiently convert T4 to T3.
If your doctor has prescribed a desiccated thyroid product, there isn't necessarily a "best" one. Product choice in most cases is simply based on patient/doctor preference and availability.
According to the most recent guidelines, the standard of care for the treatment of hypothyroidism continues to be levothyroxine (LT4). The American Thyroid Association has determined that there is no improvement of patient health outcomes with combination preparations of levothyroxine (T4)–liothyronine (T3) therapy nor thyroid extract therapy over monotherapy with levothyroxine.
The natural process in which the body produces T3 and T4 is when the hypothalamus releases Thyrotropin-releasing hormone (TRH) when thyroid hormone levels are low. The TRH elevation stimulates the release of thyroid-stimulating hormone (TSH) from the pituitary gland, which stimulates the thyroid gland to synthesize and release the thyroid hormones T3 and T4. These thyroid hormones are responsible for metabolism, growth, and development.
Symptoms of Hypothyroidism include:
- Dry skin
- Cold intolerance
- Slowed thinking
- Weight gain
- Coarse skin
- Slowed heart rate
- Delayed relaxation of ankle reflexes
Levothyroxine is synthetic T4 that is identical the thyroid hormone naturally produced by the body. Levothyroxine should be taken on an empty stomach which is why it is recommended to be taken 30 minutes before breakfast or at least 4 hours after an evening meal at bedtime with a full glass of water. When first starting levothyroxine there will be a peak of serum and free T4 levels until steady state is achieved after 6 weeks.
Levothyroxine replacement therapy has 3 main goals:
- Resolve signs and symptoms of hypothyroidism
- Normalize serum thyrotropin levels with the improvement of thyroid hormones
- Avoid over-treatment (especially in the elderly)
It is not recommended to switch between different brands or types of levothyroxine products as it could result in a variation of the administered dose. If you do decide to change to a different brand of levothyroxine it is recommended to re-evaluate the serum TSH levels after six weeks to ensure proper dosing. It is best to separate taking levothyroxine with any other medications by at least 4 hours unless otherwise instructed by a doctor prevent reduced levothyroxine absorption.