Are you experiencing fatigue, hair loss, low libido or sexual dysfunction, constipation, cold hands and feet, cholesterol problems, or difficulty losing weight? You might have a thyroid problem. Your thyroid gland is important since it produces hormones that signal all the cells in your body to create energy and to grow when needed. It is responsible for stimulating energy production and determining how many calories you burn every day. In this article, I will be writing about the importance of a healthy thyroid, how it works, and what symptoms you might experience when it is not working properly.

Your Thyroid is Your Metabolism Engine


Your thyroid is like the engine of your car. It dictates how fast or slow you are moving. In your body, it dictates how many calories you burn and how fast your body produces energy. If your engine slows down, your car will slow down. In a similar way, if your thyroid slows down, your metabolism will slow down and you might feel tired. According to the American Thyroid Association, low function of the thyroid leads to lower metabolism, also called basal metabolic rate (BMR). (1) Over the years, many people reported to me that they were slowly gaining weight, for no obvious reason. Their diet and level of activity were the same. Some even complained that they were working out several times a week and had difficulty losing weight. These could all be symptoms of thyroid dysfunction. Other symptoms of hypothyroidism are: 

  • Dry skin, fatigue, cold sensitivity, constipation, and muscle cramps (2) 
  • Increase in cholesterol, low-density lipoprotein (LDL) cholesterol, and triglycerides (3)
  • Increased risk of ischemic heart disease in people of 65 years and younger (4)
  • Lower sexual function or depression (5)
  • Slow bowel movement or constipation (6)
  • Dysfunction of sugar metabolism and higher HbA1C (7)
  • Hair loss (8)
  • Chronic fatigue (9)
  • Headaches (10) *clinical observational note, occasionally reported in the morning

How does your thyroid gland work?


The thyroid stimulates each cell in your body through the thyroid hormones, called T3 and T4. These hormones are released from your thyroid and circulate in the blood to reach your cells. Most T3 and T4 are bound to proteins and are inactive, with the exception of free T3 and T4, which are able to connect to the receptor on each cell and stimulate the cells to function and produce energy. Between both hormones, T3 is more highly active. However, it is present in significantly lower amounts than T4. To keep stimulating your metabolism and for proper function, your body requires more T3. Therefore, T4 is converted to T3 in organs such as the liver, kidney, brain, and muscles. (11)

What activates your thyroid gland?


The thyroid gland is activated by the Thyroid-Stimulating Hormone (TSH). The hypothalamus secretes Thyrotropin-Releasing Hormone (TRH) which stimulates the pituitary to secrete TSH. When your pituitary detects that the thyroid gland is not producing enough thyroid hormone, the pituitary produces more TSH, which stimulates the thyroid to produce more. Deficiency of thyroid hormone is associated with dry skin, poor memory, slow thinking, depression, cognitive impairment, muscle weakness, fatigue, muscle cramps, cold intolerance, puffy eyes, constipation, and hoarseness. Some studies also reported an association with a higher risk for cardiovascular diseases, as measured by increased levels of total cholesterol and low-density lipoprotein (LDL) cholesterol, as well as reduced levels of high-density lipoprotein cholesterol. (12)

Why are most people with low thyroid function undiagnosed? 

The reason for that is simple. When complaining of thyroid symptoms, such as fatigue, weight gain, constipation, or even the presence of high cholesterol in your labs, most doctors will only test for the thyroid-stimulating hormone (TSH). This measures how much your anterior pituitary is trying to stimulate your thyroid to work. There is an assumption within the medical community that measuring how much the thyroid is stimulated is enough to determine whether it is working. Unfortunately, that is not always the case. A study published in the Journal of Nutritional & Environmental Medicine showed that, in many cases, thyroid symptoms did not correlate with levels of TSH. (12) This means that if you went to your doctor and complained of fatigue, constipation, cold hands or feet, or weight gain, measuring your TSH levels is just the “tip of the iceberg”. It won’t show the whole picture. Many patients are misdiagnosed and do not know it. Their doctors look at their labs and send them home while they still suffer from symptoms of low thyroid function.

Reverse T3 (rT3) – a powerful metabolic inhibitor


Reverse T3 is a biologically inactive form of the active hormone T3. In other words, it does not activate the cells as T3 hormone does. It simply ‘floats’ in your blood without influencing your metabolism and energy production. Another study found that rT3 is not just an inactive metabolite, but a powerful inhibitor of the conversion of T4 to T3. It is so powerful, that it is estimated to be 100 times stronger than propylthiouracil, a medication used to decrease thyroid function. If your doctor does not check other markers, it does not provide you with the whole picture and you might still suffer from symptoms. (13)

In the next article, I will show you what to look for to make sure that your thyroid and metabolism are working properly.

Tal Cohen, DAOM, MS-HNFM is an author, presenter, and the Educational Director of the American Academy of Functional Health. He is the author of several books and patient guides, including ‘Treating Pain and Inflammation with Functional Medicine: The Complete Clinical Guide’ and ‘The Complete Guide to Removing Toxins & Improving Your Health.’ Tal completed a Master of Science in Human Nutrition and Functional Medicine and a Doctorate in Acupuncture and Oriental Medicine. 


  1. Thyroid & Weight. American Thyroid Association. Accessed 2016.
  2. Garber JR, Cobin RH, Gharib H et al. Clinical practice guidelines for hypothyroidism in adults: cosponsored by the American Association of Clinical Endocrinologists and the American Thyroid Association. Thyroid 2012; 22: 1200–35.
  3. Asvold BO, Vatten LJ, Nilsen TI, Bjoro T. The association between TSH within the reference range and serum lipid concentrations in a populationbased study. The HUNT Study. Eur J Endocrinol 2007; 156: 181–6.
  4. Razvi S, Shakoor A, Vanderpump M et al. The influence of age on the relationship between subclinical hypothyroidism and ischemic heart disease: a metaanalysis. J Clin Endocrinol Metab 2008; 93: 2998–3007
  5. Krysiak, R., Drosdzol-Cop, A., Skrzypulec-Plinta, V., & Okopien, B. (2015). Sexual function and depressive symptoms in young women with thyroid autoimmunity and subclinical hypothyroidism. Clinical Endocrinology, 84(6), 925-931. doi:10.1111/cen.12956.
  6. Bassotti G, Pagliacci MC, Nicoletti I, Pelli MA, Morelli. Intestinal pseudoobstruction secondary to hypothyroidism. Importance of small bowel manometry. A J Clin Gastroenterol. 1992 Jan; 14(1):56-8.
  7. Makadia, M. G. (2017). Study of Glycated Haemoglobin (HbA1c) In Non-Diabetic Subjects with Subclinical Hypothyroidism. Journal Of Clinical And Diagnostic Research. doi:10.7860/jcdr/2017/22600.9479
  8. Sarris, J., & Wardle, J. (2014). Clinical naturopathy: an evidence-based guide to practice. Chatswood, N.S.W.: Elsevier Australia.
  9. Ruiz-Núñez, B., Tarasse, R., Vogelaar, E. F., Janneke Dijck-Brouwer, D. A., & Muskiet, F. (2018). Higher Prevalence of “Low T3 Syndrome” in Patients With Chronic Fatigue Syndrome: A Case-Control Study. Frontiers in endocrinology, 9, 97.
  10. Lisotto, C., Mainardi, F., Maggioni, F., & Zanchin, G. (2013). The comorbidity between migraine and hypothyroidism. The Journal of Headache and Pain14(Suppl 1), P138.
  11. Mcdermott, M. T. (2001). Subclinical Hypothyroidism Is Mild Thyroid Failure and Should be Treated. Journal of Clinical Endocrinology & Metabolism, 86(10), 4585-4590. doi:10.1210/jc.86.10.4585
  12. Douglas J. Fort, Sigmund Degitz, Joseph Tietge, Leslie W. Touart. (2007) The Hypothalamic-Pituitary-Thyroid (HPT) Axis in Frogs and Its Role in Frog Development and Reproduction. Critical Reviews in Toxicology 37:1-2, pages 117-161. 
  13. Chopra, I. J. (1977). A Study of Extrathyroidal Conversion of Thyroxine (T4) to 3,3′,5-Triiodothyronine (T3) in Vitro*. Endocrinology, 101(2), 453-463. doi:10.1210/endo-101-2-453

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