The Basics
Hypothyroidism is a condition that occurs when the body doesn’t produce enough thyroid hormone. Thyroid hormones travel throughout the body and affect almost every system, including the nervous system, cardiovascular system (heart and blood vessels), digestion, and the immune system. Hypothyroidism symptoms include fatigue, brain fog, depression, constipation, dry skin, hair loss and weight gain.
Thyroid hormones are made in the thyroid gland, which is located in the front of the neck just above the chest. There are 2 thyroid hormones, levothyroxine (T4) and liothyronine (T3) - T3 is the active form and is made from T4. To produce thyroid hormones, the brain releases the hormone TSH (thyroid stimulating hormone). When enough T4 and T3 have been made, they signal to the brain to stop producing TSH.
This is how labs look for various thyroid conditions:
| TSH | T4 | T3 |
Hypothyroidism | High | Low | Low |
Subclinical Hypothyroidism | High | Normal | Normal |
Hyperthyroidism | Low | High | High |
The optimal level of these labs has been a controversial point recently, with the ideal levels looking quite different than typical "normal" ranges listed on lab testing. Lab tests consider any TSH value between about 0.5 and 4.5 to be normal. However, more recently we are finding that levels between 1 and 2 are preferred (and even better when closer to 1). At this range, symptoms of hypothyroidism tend to be better managed, and people just feel better.
Now - how thyroid hormones affect the rest of the hormones in the body:
Insulin & Thyroid
Thyroid hormones play an important role in blood sugar (glucose) management by stimulating the release of insulin. The role of insulin is to help move glucose from the blood into storage. Dysfunction with insulin can result in too much glucose staying in the system, and ultimately leads to diabetes.
It has been well-documented that hyperthyroidism (over-active thyroid) results in insulin resistance as the excess thyroid hormones stimulate the release of too much insulin. However, newer research shows that hypothyroidism can also result in high insulin levels and insulin resistance.
Hypothyroidism reduces the ability of the body to respond to insulin. As more glucose builds up in the system, the body tries to keep up by producing more and more insulin. This high level of insulin is the hallmark of insulin resistance. Without treatment, insulin resistance can lead to diabetes and cardiovascular or heart disease. With proper treatment and hormone replacement, insulin sensitivity can improve, meaning the body starts to respond to insulin properly again, and the insulin levels start to drop back into normal range.
Cortisol & Thyroid
Cortisol is typically the hormone associated with stress. During times of stress - physical or psychological - the adrenals release cortisol, which helps the body manage stress by increasing energy production, heart rate and blood pressure. Essentially, the body is getting prepared to deal with a potential threat, (i.e. fight or flight). Short-term elevations are normal and protective, though when we experience persistent elevations in cortisol, this can have detrimental health effects.
Where does hypothyroidism come in? Hypothyroidism is associated with elevated cortisol. This means that when poorly managed, and thyroid hormone levels remain low, cortisol will be persistently elevated. This can result in fatigue, irritability, digestive symptoms and weight gain.
Estrogen, Progesterone, Testosterone & Thyroid
All of the sex hormones bind to a protein called SHBG (sex hormone binding globulin), and when bound are effectively inactive. The “free” forms of estrogen, progesterone and testosterone, that are not bound to this protein, are what actually affect the body. Estrogen and progesterone dominate in women, and testosterone dominates in men, though both men and women have and need all 3 hormones.
With hypothyroidism, the levels of SHBG increase and causes there to be less circulating sex hormones. Testosterone, which binds to this protein the best, tends to be affected the most, resulting in low testosterone in both men and women. Symptoms of low testosterone include fatigue, low libido and loss of muscle mass. Estrogen and progesterone activity decrease as well, though this effect is typically only seen in women. Symptoms of estrogen and progesterone imbalance include heavy and/or irregular periods, painful periods, fibroids, migraines, low libido, and weight gain.
The Takeaway
Hypothyroidism mainly affects thyroid hormones, though it can also affect every other major hormone in the body. The body is a complex system and there are often downstream and cascading health effects that can result from any disease. Staying healthy means taking a deeper look into the body as whole, making sure all areas of imbalance are addressed. It’s also important to recognize that all bodies are unique, and hormone imbalances can look different in different people. If you’re looking to take some steps toward full body health, it’s essential to find a health care provider that you can work with to develop a personalized treatment plan as unique as you are.
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Disclaimer
The information provided in this blog and throughout the website is intended for educational purposes only and should not be considered, or used as a substitute for, medical advice. The content is not meant to diagnose, treat, or cure any medical condition. This blog does not constitute the practice of any medical, nursing or other professional health care advice, diagnosis or treatment. Always consult with a qualified healthcare provider before making any changes to your health regimen or starting new treatments, and never disregard professional medical advice or delay seeking care because of something that you have read on this blog, website or in any linked materials. Your individual needs and circumstances should be evaluated by a medical professional to ensure safe and appropriate care. If you are experiencing a medical emergency, please call 911 or call for emergency medical help on the nearest telephone immediately.
References
Biondi, Bernadette, George J Kahaly, and R Paul Robertson. “Thyroid Dysfunction and Diabetes Mellitus: Two Closely Associated Disorders.” Endocrine Reviews 40, no. 3 (January 14, 2019): 789–824. https://doi.org/10.1210/er.2018-00163.
Brenta, Gabriela. “Why Can Insulin Resistance Be a Natural Consequence of Thyroid Dysfunction?” Journal of Thyroid Research 2011 (2011): 152850. https://doi.org/10.4061/2011/152850.
Kjaergaard, Alisa D., Eirini Marouli, Areti Papadopoulou, Panos Deloukas, Aleksander Kuś, Rosalie Sterenborg, Alexander Teumer, et al. “Thyroid Function, Sex Hormones and Sexual Function: A Mendelian Randomization Study.” European Journal of Epidemiology 36, no. 3 (March 1, 2021): 335–44. https://doi.org/10.1007/s10654-021-00721-z.
Ren, Bingtao, and Yan Zhu. “A New Perspective on Thyroid Hormones: Crosstalk with Reproductive Hormones in Females.” International Journal of Molecular Sciences 23, no. 5 (February 28, 2022): 2708. https://doi.org/10.3390/ijms23052708.
Saran, Sanjay, Bharti Sona Gupta, Rajeev Philip, Kumar Sanjeev Singh, Sureshrao Anoop Bende, Puspalata Agroiya, and Pankaj Agrawal. “Effect of Hypothyroidism on Female Reproductive Hormones.” Indian Journal of Endocrinology and Metabolism 20, no. 1 (2016): 108–13. https://doi.org/10.4103/2230-8210.172245.
Vyakaranam, Sapna, Swati Vanaparthy, Srinivas Nori, Satyanarayana Palarapu, and Aparna Varma Bhongir. “Study of Insulin Resistance in Subclinical Hypothyroidism.” International Journal of Health Sciences and Research 4, no. 9 (September 2014): 147–53.