It is important to keep the thyroid properly regulated, because it affects so many metabolic processes in the body. The herbs discussed here are useful for regulating the gland and hormone pathways.

Thyroid disease is very common in cats, dogs and even horses. It is important to properly diagnose and treat thyroid disease, as thyroid hormone affects almost every organ in the body.

Physiological pathway

The hypothalamus produces TSH-releasing hormone (TRH), which travels to the anterior pituitary. The pituitary then produces thyroid-stimulating hormone (TSH), which stimulates the thyroid gland. The thyroid gland makes primarily thyroxine (T4) and some triiodothyronine (T3). Most T3 is made in the peripheral tissues via the deionization of T4. T3 is the bio-active thyroid hormone. Both T3 and T4 are stored in the thyroid gland and transported through the blood stream bound to a protein. The protein is easily released when the hormone is transported into the receptor cell. Free T4 or T3 in the blood (unbound to a protein) provides the negative feedback loop to the hypothalamus and pituitary to stop their production of TRH and TSH, respectively. T3 receptors are found in both the nucleus and mitochondria of cells. T3 and T4 are inactivated via the irreversible removal of an inner-ring iodine catalyzed by type 3 deiodinase (D3).

Given this intricate pathway, thyroid disorders can occur in a myriad of locations and ways, causing a variety of symptoms. Problems with the hypothalamus or pituitary, issues with the synthesis of TSH or TRH, defi ciencies of albumin or globulin (the carrier proteins) all affect the thyroid. Complete bloodwork including a full thyroid panel is the most accurate way to diagnose thyroid hormone abnormalities.

Hyperthyroidism

Cats tend to become hyperthyroid, while dogs and horses become hypothyroid. The diseases generally manifest with age, so testing becomes more important as any animal gets older. Clinical signs of hyperthyroidism include reduced insulin sensitivity, tissue atrophy, increased energy expenditure at rest and exercise, elevated heart rate and palpitations, anxiety and increased thermogenesis. There are also changes at the genetic level: glucose and lipid metabolism, protein synthesis, transcriptional control, signal transduction and mitochondrial energy metabolism via increased mitochondrial uncoupling protein 3 (UPC3). This uncoupling causes a 70% increase in the citric acid (TCA) cycle but no increase in adenosine triphosphate (ATP) synthesis. Thyroid adenoma is the most common cause of hyperthyroidism in cats, but another frequent cause is carcinoma.

Hypothyroidism

Dogs can truly become hypothyroid. Horses are often supplemented with thyroid powder without proper diagnostic testing, which can cause iatrogenic hypothyroidism. Clinical signs of hypothyroidism include weight gain despite inappetance, fatigue, feeling cold all the time, bradycardia, shortness of breath, pericardial, pleural and abdominal effusions, poor memory and concentration, and constipation. In dogs, lymphocytic thyroiditis and idiopathic thyroid gland atrophy are the most common causes of hypothyroidism, but diseases of the pituitary or hypothalamus can also cause secondary hypothyroidism.

Herbal help

Most of the herbs discussed below don’t specifically treat “hyperthyroidism” or “hypothyroidism”, but instead regulate the gland and hormone pathways as a whole. Since thyroid disease is so common, there are many herbs that affect the thyroid along with a plethora of research.

1. Melissa officinalis

Also known as lemon balm or bee balm, this member of the Lamiaceae family is a commonly used medicinal herb. As with most mints, its aerial parts are used medicinally. Lemon balm inhibits TSH receptor binding, which causes decreased production of T3 and T4 in the thyroid gland.¹ It decreases circulating TSH levels² but increases levels of circulating T3 and T4.³ This is due to the negative feedback loop in which increased circulation of free T3 and T4 goes to the pituitary and causes decreased production of TSH.

“Melissa officinalis increases the level of thyroid hormones probably through increasing albumin synthesis, decreasing fat levels, and eventually decreasing leptin hormone levels. This extract also reduces TSH level probably due to the negative feedback of thyroid hormones.”⁴ In other words, albumin is one of the proteins that transport thyroid hormone through the bloodstream. “Fats and thyroid levels have an inverse and significant relation. Since M. officinalis extract can reduce blood lipid levels, it is most likely that at least part of this effect is exerted by increasing thyroid hormone.”³ Leptin is secreted from fat cells and binds to receptors in the hypothalamus. “Its main physiological role is decreasing weight via reducing appetite for food and increasing the production of energy from body fat reserves.”⁴ When the fat level is decreased, there is less fat to produce leptin, so the leptin levels would “eventually” decrease.

2. Nigella sativa

Black seed or black cumin, as it is commonly known, has been used medicinally for thousands of years in Arabian and Indian traditions. Black seed has biochemical and histologic effects on thyroid hormone and the thyroid gland, respectively. It increases circulating T4 levels⁵ and circulating levels of T3. It also increases the ratio of T4:T3.⁶ This is because it increases T4 levels more than T3 levels, so the ratio adjusts. Again, the negative feedback loop leads to decreasing circulating levels of TSH.⁷ Histologically, it protects thyroid tissue from hyperplastic changes secondary to hypothyroidism⁷ so the thyroid can function more normally.

3. Commiphora mukul

Guggul is a member of the Burseraceae family; its oleogum resin is the part used medicinally. Guggul increases the uptake of iodine by the thyroid gland,⁸ enhances the activity of thyroid peroxidase enzyme (an iodine liberating enzyme) and protease,^8,9 increases T3 production, and generally stimulates the thyroid gland.⁹ Increased T3 production is due to increased conversion of T4 to T3 in the liver: “Guggulsterone also seems to increase T3 synthesis by increasing the conversion of T4 to T3 and significantly decrease hepatic lipid peroxidation. Since serum thyroxine (T4) is converted to T3 in the liver, researchers concluded that hormone levels and peroxidation are related.”¹⁰

4. Fucus vesiculosus

Bladderwrack or kelp is a brown seaweed of the Fucaceae family. It is tempting to think that it’s only the iodine content of kelp that affects the thyroid, but it has other influences as well. “Brown seaweeds are the only known non-animal sources of thyroid hormones. The presence of organically-bound iodine in brown seaweeds as thyroid hormones may explain some of the effects of eating some brown seaweeds…. Fucus species of brown seaweeds have been used as treatment for thyroid disorders. The thyroid hormone present in Fucus is Di-Iodothyronine (DIT); it is weakly active if at all as a thyroid hormone in the mammalian body. Two DIT molecules are condensed in an elegant esterification reaction to produce tetraiodotyrosine (T4, thyroxine). The organically bound iodine in Fucus may enhance T4 production by providing some prefabricated portions of T4…. The therapeutic effects of using powdered Fucus…resemble the therapeutic effects of thyroxine medications.”¹¹ So the body takes the DIT molecules in the kelp and turns them into T4 for use.

Effects of kelp on the thyroid gland

Rezk et al studied the histology of the thyroid gland with radiation and kelp. They broke study rats into four groups:

1. A control group
2. A Fucus vesiculosus group in which the rats were given 100 mg/kg kelp for 30 days
3. An irradiation group where the rats were irradiated once with 4Gy
4. A combination of 2 and 3 in which the last dose of kelp was administered 60 minutes prior to irradiation.

The rats were “sacrificed” seven and 15 days post irradiation. On day seven, Group 3 had “ruptured follicular epithelial cells, ruptured colloid, disappearance of parafollicular cells, and edema. Also, on the 15th day, most follicular cells were disappeared.”12 In Group 4, the kelp normalized the follicular cells in the thyroid gland histologically, and returned the follicles to normal variations of shape and size. In this study, kelp also stabilized T3 and T4 levels in irradiated rats.

There are many other herbs that affect the thyroid gland and all the hormones involved in its metabolic process. It is very important to keep the thyroid properly regulated, as it affects so many metabolic processes in the body.

References

¹Wynn S, Fougere B. Veterinary Herbal Medicine. St. Louis: Mosby Elsevier, 2007.

²Duke J. The Green Pharmacy. New York: St. Martin’s Press, 1997.

³Zarei A, Changizi-Ashtiyani S, Taheri S, Hosseini N. “A Brief Overview of the Effects of Melissa officinalis L. Extract on the Function of Various Body Organs”. Zahedan Journal of Research in Medical Sciences, 29-34, 2015.

⁴Zarei A, Changizi-Ashtiyani S, Rezaei A, Taheri S. “Comparison Between the Effects of the Alcoholic Extract of Melissa officinalis and Atorvastatin on Serum Levels of Thyroid Hormones in Hypercholesterolemic Male Rats”. Zahedan Journal of Research in Medical Sciences, 6-12, 2013.

⁵Sharif S, Elmahdi B, Mohammed A, Mohammed A. “The Effects of Nigella sativa L. Ethanolic Extract on Thyroid Function in Normal and Alloxan-Induced Diabetic Rats”. Thyroid Research and Practice 9 (2), 48-52, 2012.

⁶Habeeb A, El-Tarabany A. “Effect of Nigella sativa or Curcumin on Daily Body Weight Gain, Feed Intake and some Physiological Functions in Growing Zaraibi Goats during Hot Summer Season”. Arab Journal of Nuclear Science and Applications 45 (2), 238249, 2012.

⁷Khalawi A, Al-Robai A, Khoja S, Ali S. “Can Nigella sativa Oil (NSO) Reverse Hypothyroid Status Induced by PTU in Rat?” Biochemical and Histological Studies. Life Science Journal 10 (2), 802-811, 2013.

⁸Stansbury J, Saunders P, Winston D. “Promoting Healthy Thyroid Function with Iodine, Bladderwrack, Guggul and Iris”. Journal of Restorative Medicine 1 (1), 8390, 2012.

⁹Shishodia S, Harikumar K, Dass S, Ramawat K, Aggarwal B. “The Guggul for Chronic Diseases: Ancient Medicine, Modern Targets”. Anticancer Research 28, 3647-3664, 2008.

¹⁰Friedman M. “Thyroid Autoimmune Disease”. Journal of Restorative Medicine 2 (1), 1-13, 2013.

¹¹Kandale A, Meena A, Rao M, Panda P, Mangal A, Reddy G, Babu R. “Marine Algae: An Introduction, Food Value and Medicinal Uses”. Journal of Pharmacy Research 4 (1), 219-221, 2011.

¹²Rezk R, El-Azime A, Sh A. “Fucus vesiculosus Ameliorates Histological and Biochemical Changes in Thyroid Gland and Ovary of Irradiated Rats”. Arab Journal of Nuclear Science and Application 46 (3), 286-296, 2013.

AUTHOR PROFILE

Laurie Dohmen, VMD, MS

Dr. Laurie Dohmen graduated from the University of Pennsylvania. She is trained in acupuncture, food therapy, Back flower essences, and most extensively in Western herbs. She recently downsized her integrative mixed animal practice in Delaware, and lectures regularly on Western herbal veterinary medicine and other holistic topics. Dr. Dohmen is also on the faculty of Maryland University of Integrative Medicine, from which she received her Master's in Therapeutic Herbalism. She is currently president of the Veterinary Botanical Medical Association.