Tom Morrione, MD examines the history of the thyroid and the causes and diagnoses for hypothyroidism.

by Tom Morrione, MD

Which one of the following would you most likely prescribe for treating hypothyroidism? (excluding thyroid hormone replacement therapy)?

Poll Results:
Selenium 14%
L-Carnitine 9%
Seaweed 14%
Iodine 46%
Vitamin D 17%

The thyroid gland was one of the first endocrine organs to have a recognized and treated deficiency.  Individuals lacking a thyroid gland were noted to develop both mental and growth deficits called cretinism.  Treatment for this condition began in 1891 with the thyroid extracts, a form of hormone replacement therapy (HRT).  Two active thyroid hormones, triiodothyronine (T3) and tetraiodothyronine (T4) are produced and secreted by the thyroid gland.  T3 is the more active of the two but almost all the output from the gland is in the form of T4.  Target tissues contain enzymes to convert T4 to T3.  Though diabetes is climbing rapidly in the United States, thyroid disorders remain one of the most common endocrinopathies affecting 4-5%, and even higher worldwide.
Causes of hypothyroidism are several and include: an interruption or influence on the hypothalamic-pituitary axis where thyrotropin-releasing hormone (TRH) or thyroid-stimulating hormone (TSH) are produced such as a pituitary tumor; a dietary deficiency of iodine needed to manufacture T3 and T4; an autoimmune destruction of the thyroid gland where the antibodies either attack the gland itself or block hormone synthesis; or surgical resection or radioactive iodine treatment for hyperthyroidism removing most, if not all, T3 and T4 production.  There is no widely accepted screening recommendation and the diagnosis begins clinically with symptoms of cold intolerance, sleepiness, weight gain, constipation and hair loss confirmed with laboratory tests showing decreased levels of T3 and T4 and TSH is often increased but may also be decreased depending on the cause.  A patient may have subclinical hypothyroidism with an elevated TSH but normal levels of T4.

 Upon diagnosing hypothyroidism, the standard of treatment remains either synthetic or natural hormone replacement therapy (made from desiccated pig thyroid glands).  Additionally, there is evidence for some of the therapies listed in the poll for the treatment of hypothyroidism. 

 With both Iodine and Vitamin D, there is strong scientific evidence.  Iodine, the most popular choice, at 46%, is required to synthesize T3 and T4 in the follicular epithelial cell via peroxidase to thyroglobulin.  The most common physical presentation of iodine deficiency is a goiter and is prevalent worldwide in areas with known iodine deficiency.  In the United States, the table salt has been iodized and cattle feed also fortified to prevent deficiencies.  Urine tests, pre and post a challenge of iodine, help to identify iodine deficiency and can be considered in hypothyroidism and is strongly recommended prior to treating empirically.  Supplementation should be monitored under the supervision of a healthcare provider.

 The second most popular choice was Vitamin D, and to all those that attended the Integrative Healthcare Symposium in New York this month and had the pleasure of hearing Dr. Holick’s lecture on Vitamin D, you may already be putting all your patients on Vitamin D supplementation to prevent and treat a variety of ailments.  However, the mechanism affecting the thyroid is actually the parathyroid gland, as hypovitamitosis D often results in secondary hyperparathyroidism from vitamin D associated hypocalcemia.
 For the remaining three choices, the evidence is unclear or conflicting.  Regarding L-Carnitine there is some growing evidence for treatment of hyperthyroidism but none for hypothyroidism.  Brown Seaweed, bladderwrack, contains iodine as well as other vitamins and minerals.  Consumption may result in heavy metal poisoning with arsenic or lead.  Evidence does suggest possible use in the treatment of thyroid disorders, however, there is not an accepted known concentration of iodine within these products and, therefore, dosing and safety are undetermined.

 Lastly, Selenium is a mineral present in water, soil and a few foods and is needed in the synthesis of T3.  There is some evidence indicating benefits with treatment of thyroiditis but as with bladderwrack, dosing, safety and efficacy are still not well researched. 

Gartner R, Gasnier BC, Dietrich JW, et al. Selenium supplementation in patients with autoimmune thyroiditis decreases thyroid peroxidase antibodies concentrations. J Clin Endocrinol Metab 2002;87:1687-91. [February 2009]