Natural desiccated thyroid, often called NDT or desiccated thyroid extract, has been used since the late 1800s, and it is one of the safest drugs available. It contains a full spectrum of thyroid hormones, T4 and T3 and T2 and T1 as well. About 20% of patients taking levothyroxine (T4 only) are not happy with T4 only medication and actually feel better on NDT because it contains both T4 and T3. When considering the safety of natural desiccated thyroid, we need to look at its hormone composition, monitoring requirements, potential risks, and the quality of evidence supporting long-term treatment.
What Is a Natural Desiccated Thyroid?
Natural desiccated thyroid is made from dried and powdered porcine (pig) thyroid glands, contains both thyroxine (T4), and triiodothyronine (T3).
That combination differs from levothyroxine, which contains T4 alone. The human thyroid naturally produces both hormones. Although T4-to-T3 ratio in natural desiccated thyroid (NDT) is about the same as the ratio in the circulating blood stream.
T3 is available as Cytomel and is the more biologically active component. T4 must be converted to T3 to become biologically active. T3 and has a shorter half-life of 24 hours compared to about 7 days for T4.
T4 is a prohormone and must be converted inside our cells to T3 to become biologically active.
More on combination treatment with T3 and T4 can be found here: T3/T4 Combination Thyroid Therapy.
Is Natural Desiccated Thyroid (NDT) Safe Long Term?
The answer is that NDT has been widely used since 1891 when a physician named George Murray used sheep thyroid extract injections to successfully treat a patient with myxedema (severe hypothyroidism). Very few other drugs have such a long history safety and efficacy. Levothyroxine was first synthesized in 1927, and widely used starting in the 1950’s. However, levothyroxine was not FDA approved until 2001. Adverse side effects due to thyroid excess (or overdose) are similar for both types of medications, levothyroxine and NDT. Symptoms include rapid heart rate, palpitations, anxiety, insomnia, and loose stools. These adverse effects can be avoided by staying within the dosage range prescribed by your physician.
Why Including T3 Matters
About 20 percent of patients taking levothyroxine and other T4 medications do not feel well, and will report continued hypothyroid symptoms, even though their TSH remains within the normal range. These patients do much better by switching to NDT which contains both T3 and T4.
How Is NDT Monitored?
A complete thyroid laboratory panel includes TSH, Free T3, Free T4, reverse T3 and anti-thyroid antibodies. Although TSH is commonly used to monitor dosage, the TSH is sometimes unreliable and the thyroid hormone levels (Free T3 and Free T4, and reverse T3) may be more useful.
Laboratory values should be interpreted in light of patient symptoms. Thyroid excess should be considered with symptoms such as palpitations, sweating, tremors, anxiety, and insomnia.
How often do we check thyroid levels on NDT? We check thyroid labs at 6-week intervals when starting NDT or when changing dosage. Once maintained dosage has stabilized, labs can be done less frequently every 6 months.
IS “Natural Thyroid” Better than Levothyroxine?
NDT is an established thyroid hormone preparation, and some patients report preferring it. Most people on Levothyroxine do well with it. However, about 20 per cent of people on levothyroixine are poor converters, meaning they remain hypothyroid in the periphery even though the TSH is within the normal range. These patients feel much better when switching to NDT. So, YES, NDT is better for some patients.
At TruemedMD, our medical director, Jeffrey Dach MD, devotes his full attention to the clinical history, thyroid related symptoms, laboratory results, and response to treatment. The goal is complete relief of hypothyroid symptoms.
Frequently Asked Questions
Can you take thyroid medication for life?
Yes. Some patients, such as those after complete thyroidectomy will need thyroid medication for life. And some patients with less severe forms of thyroid disease may be able to reduce dosage and gradually stop the thyroid medication over time.
Which Patients are Not Good Candidates for NDT?
Patients taking NDT must have good cognitive function and must be able to recognize signs of thyroid excess and take a break from the medication if this occurs. This is why dementia patients and young children are not good candidates for NDT.
Does Thyroid Medication cause heart problems?
Excess thyroid hormone from any type of thyroid medication may increase the heart rate (tachycardia) and may cause abnormal cardiac rhythm (atrial fibrillation) making dosage and patient monitoring important for long term treatment.
Can Thyroid Medication Affect Bone Health?
Excess thyroid hormone from Grave’s disease or from excessive thyroid medication dosage may contribute to bone loss over time, particularly when treatment causes hyperthyroidism with elevated Free T3 and Free T4. Suppression of TSH is commonly seen with combination T3 and T4 medication. Studies in thyroid cancer patients after thyroidectomy show that long term suppression of TSH by itself, without any elevation of Free T3 and Free T4 has no harmful effects on bone density.
Should I stop NDT if I am concerned?
Do not stop or change thyroid medication on your own. Discuss your concerns with your healthcare professional so changes can be made safely.
Deciding on Thyroid Treatment
If you currently take Levothyroxine and you are interested in exploring NDT, our medical director at TruemedMD, Jeffrey Dach, MD, can review your symptoms, laboratory results, treatment history, and treatment options with you. A thoughtful clinical evaluation can determine if NDT would be a good choice for you. For more information about NDT, see Dr. Dach’s book on natural desiccated thyroid, Natural Thyroid Toolkit.
Articles with Related Interest:
Combination T3 and T4 Reduces Mortality and Dementia
Errors in Modern Thyroid Endocrinology
Natural Thyroid is Better part Two
New Study Shows Natural Thyroid is Better
