If you have thyroid disease, you may experience some fluctuations in your thyroid hormone levels from time to time. These fluctuations can occur as your thyroid disease progresses, but other factors, such hormonal changes, and medication variations, can alter your thyroid hormone levels as well, producing a variety of symptoms.
The Changing Course of Your Thyroid Disease
Thyroid disease can progress or stabilize as the years go on, either due to the natural course of the condition itself or to major changes triggered by the treatment (such as surgical removal of the thyroid gland).
Hashimoto’s Thyroiditis
Hashimoto’s thyroiditis often progresses over the first 10 years. After diagnosis and treatment are established, thyroid antibodies may continue to further attack the thyroid gland, making it less and less able to produce thyroid hormone on its own. Therefore, even if you maintain the same treatment dose, your thyroxine (T4) and triiodothyronine (T3) thyroid hormone levels can drop, causing your thyroid-stimulating hormone (TSH) to rise in response.2 Overall, you may feel the symptoms of hypothyroidism, including fatigue, weight gain, and depression.
Graves’s Disease
Graves’ disease can also progress, especially in the first few years after diagnosis. In many instances, even when your treatment is at the right dose, your T3 and T4 levels may continue to rise, your TSH may fall, and you can develop symptoms of hyperthyroidism, such as the inability to concentrate, insomnia, and weight loss. With Grave’s disease, the opposite can happen, too. In some cases, after months or years of taking antithyroid medications, your condition can go into remission, your T3 and T4 levels may decrease (while your TSH rises), and you can develop symptoms of hypothyroidism.
Thyroiditis After Pregnancy
Some women develop thyroiditis after pregnancy.4 Usually, this is characterized by low thyroid hormone levels and high or low TSH, but high thyroid hormone levels with low or high TSH can develop as well. Pregnancy can affect thyroid hormones in many ways, and the changes in these levels are more extreme if you already have a thyroid condition prior to becoming pregnant.
Medication Potency Differences
If you’ve started taking prescription thyroid hormone replacement medication from a newly refilled prescription or from a different pharmacy, your thyroid hormone blood levels may change. If you’re stabilized, shifting to another brand or getting refills of generics from different manufacturers can cause some swings in your levels because of the different potencies of each product. Depending on your condition, these potency variations can cause mild increases or decreases in your T4, T3, or TSH, as well as corresponding symptoms of hypothyroidism or hyperthyroidism.
When and How You Take Your Pill
If you’re taking your thyroid replacement or antithyroid medication at different times each day, you might not be consistent about taking it on an empty stomach as recommended.1 Food may delay or reduce the drug’s absorption by changing the rate at which it dissolves or by changing the stomach’s acid balance, ultimately affecting your thyroid hormone levels, your symptoms, and your test results. If you want to ensure the best possible absorption of your medication, take your thyroid medication consistently. Ideally, you should take your thyroid medicine in the morning, on an empty stomach, about one hour before eating breakfast and drinking coffee, or at bedtime (three hours after the last meal).1
Also, make sure to wait for at least three to four hours between taking thyroid medication and taking any fiber, calcium, or iron-rich foods or supplements, as they can prevent you from absorbing your full dose of medication.
Other Medications and Herbs
Some herbal supplements and medications can have an impact on thyroid hormone levels, either by competing with the body’s thyroid hormone activity, amplifying the effects of thyroid hormones, or altering medication absorption and activity. Some medications that may affect thyroid levels include certain cholesterol-lowering drugs, corticosteroids, growth hormone, lithium, and amiodarone. It is best to ask your pharmacist and doctor about potential interactions.
Change of Seasons
Thyroid levels and TSH, in particular, can change along with the seasons.8 TSH naturally rises somewhat during colder months and drops back down in the warmest months. Some doctors adjust for this by prescribing slightly increased dosages during colder months and reducing dosage during warm periods.
Reference
https://www.verywellhealth.com/when-your-thyroid-levels-are-fluctuating-3232909
