When diagnosed with an underactive thyroid, patients require some type of intervention to kick-start their metabolism or risk the consequences of an under performing thyroid. This intervention is usually in the form of Levothyroxine and patients can take artificial thyroid enzymes to make up for their deficiency . In a subset of patients, their TSH levels (the hormone used to gauge hypothyroidism) may not be high enough to warrant an outright diagnosis of hypothyroidism and these patients will leave the medical office with a condition termed subclinical hypothyroid. If diagnosed with this condition, we use a "watch and wait" approach in medicine generally where we wait for patients to develop hypothyroidism outright before prescribing medication . This "watch and wait" approach may not sound ideal for patients but inactivity from physicians does not mean that patients have no hand in determining their fate. Various supplements for hypothyroidism are available that patients can try to correct their thyroid dysfunction.
Do Supplements for Underactive Thyroid Work?
The first thing that a patient considering taking some type of supplement for their underactive thyroid must consider is if these supplements will do more harm than good. Unfortunately, a lot of products released on an "over-the-counter" basis do not undergo the same type of rigorous testing that medications requiring prescriptions much pass so you have to be careful that you are not "adding fuel to the fire" . Even if these medications are much cheaper, patients must realize that physicians do not have secret contracts with pharmaceutical companies when writing prescriptions and a more expensive product will almost always work more effectively than an "over-the-counter" product.
One study put these supplements for hypothyroidism to the test to determine if they have thyroid hormones already added to the packaging.
This surge of excessive thyroid hormone into the body will do more harm than good and patients risk developing hyperthyroidism, increase their risk of thyroid cancer and may even permanently ruin their thyroid function all because of their decision of taking supplements. They also accelerate their bone depletion and can develop osteoporosis at a much younger age.  As you can see, having a mild of subclinical hypothyroidism can balloon very quickly to something much more severe if patients are not aware of exactly what they are putting into their bodies. If you are unsure, ask an expert.
Supplements to Consider for Your Underactive Thyroid
- Zinc is an element that is imperative for your thyroid function.
Studies find that those that have zinc deficiencies will have an accompanying underactive thyroid because zinc is directly responsible for activating thyroid hormones. One study documented the effects of zinc supplementation in two participants who had low levels physiologically. Participants took daily zinc supplementation and at the end of a 4-month study, it was found that participants had a significant increase in T3 (the active compound of thyroid) as well as an increase in their resting metabolic state. 
- Another essential supplement for hypothyroidism comes in the form of selenium.
Selenium is an element that also has a strong relationship with a thyroid functioning properly and much research has been done in the last decade unlocking some of the mysteries it can solve. Physicians have found that even small amounts of selenium supplementation have a noticeable effect on the anti-thyroid antibodies that cause Hashimoto's thyroiditis (autoimmune hypothyroidism). Selenium is able to also improve the shape and size of the thyroid gland and help patients return to a state of normality without the dangerous side effects of other supplements on the market. 
- The last supplement for hypothyroidism worth mentioning comes in the form of a preparation that patients can purchase "over-the-counter." This compound goes by the name Armour Thyroid and is a preparation of desiccated thyroid hormone.
This is a preparation that is based on the physiological release of thyroid naturally in the body and studies find that patients with subclinical hypothyroidism respond better with this preparation compared to standard Levothyroxine therapy .Further studies show that patients that take this supplement note marked improvement in a variety of complications of hypothyroidism such as fatigue, constipation, weight gain and hair loss.  The quantities of artificial thyroid hormones are also balanced so you will never exceed the daily allotment that may be possible if you purchase other "over-the-counter" supplements.