What Role Does Progesterone Play in Thyroid Function?

Do you have heavy menstrual bleeding, depression, fatigue, and headaches? Are you anxious, irritable, moody, can’t sleep, have pain and inflammation? And on top of all this, you can’t lose those stubborn, unwanted pounds! These are common symptoms of progesterone deficiency. These same symptoms are also characteristic of hypothyroidism.   The reason why many women develop hypothyroidism during peri- and menopausal stages is that they lose progesterone, a vital hormone that activates an important enzyme responsible for thyroid function.

Natural progesterone is the hormone produced by a woman’s ovary. It is not the synthetic version commonly dispensed by pharmacies as tablets with a prescription such as Provera® (medroxyprogesterone). Progesterone does more than just maintain the endometrium in pregnancy. The regulation of blood pressure, sugar metabolism, fat conversion, estrogen production, new bone formation are among some of its important functions in the female body. Progesterone is anabolic (burns fat) and thermogenic (increases energy) so that a deficiency causes weight gain and low temperature.

The Interplay between Estrogen and Progesterone

Many women have estrogen excess because they lose progesterone long before menopause, and estrogen and progesterone need to fit into a nice ratio, according to Dr. Pamela Smith, the director of Fellowship in Anti-Aging and Functional Medicine. Dr. John Lee, a pioneer in bio-identical hormone therapy, reasons that thyroid and estrogen oppose each other. Estrogen causes food to be stored as fat. Thyroid hormone causes fat to be burned as energy. Patients with “normal” thyroid hormone levels measured by blood tests have symptoms that suggest they have hypothyroidism. When these patients are given progesterone, which is known to oppose estrogen, their hypothyroid symptoms improve. This implies that too much estrogen in the body (estrogen dominance) interferes with thyroid hormone action.

Estrogen excess is common in women going through the “change” due to a dip in progesterone, as well as women taking estrogen-only hormone replacement therapy. Many women receive estrogen pills when they complain about hot flashes. It is important to note that hot flashes can be caused by other factors other than estrogen deficiency such as impaired elimination of estrogen, low progesterone levels, stress, lack of exercise, and diets that are low in grains and fibers. Environmental estrogens found in our meats and in plastics can create excess estrogens in our body as well. Without adequate natural progesterone to counterbalance (progesterone is an anti-estrogen), women end up with too much estrogen.

Estrogen metabolism changes after menopause, and consequently a woman may respond differently to estrogen replacement. With age, a sluggish liver may slow estrogen metabolism, which can cause estrogen to accumulate and create estrogen dominance. Furthermore, some estrogen metabolites that are accumulated and recirculated in our body can have a very negative impact on breast and heart health.

The Thyroid-Progesterone Connection

The thyroid gland, largest of the endocrine glands, is the body’s metabolic thermostat. It regulates body temperature and the rate of energy production, which greatly influences the rate at which all body organs function. Progesterone and thyroid hormones are intimately connected. Progesterone improves the signaling mechanisms and also stimulates the production of TPO, the enzyme involved in making thyroid hormones. Too little progesterone depresses TPO activity, lowering the production of thyroid hormones.

The symptoms of progesterone deficiency and hypothyroidism can be very similar. A female in the premenopausal stage is still producing a sufficient amount of estrogen (menstruation indicates adequate estrogen) and as her progesterone levels decline she becomes estrogen dominant. Most women in this phase are not being tested for progesterone levels since they still have regular periods. Also, her T3 and T4 (thyroid hormones) levels appear normal but she’s presenting with fatigue and low basal temperature, both of which are indicators of hypothyroidism.

Hormone balancing is a complex and intricate web. Thyroid hormones are interconnected with ovarian hormones like estrogen and progesterone. Keep in mind that the stress hormone cortisol and pancreatic hormone insulin can also play a part in hormone homeostasis. If you’re between the ages of 35 and 55 and presenting symptoms of hypothyroidism, get your hormones checked to see what your estrogen to progesterone ratio looks like. You could have low progesterone levels aggravating or creating thyroid dysfunction.


Saliva testing for hormones is available at TLC Medical Centre Pharmacy. Come and get tested to find out what your baseline hormone levels are to help yourself get balanced and healthy. Begin to feel more like yourself again!!

Picture of Zoom H. Heaton

Zoom H. Heaton

TLC Medical Centre pharmacy is a traditional pharmacy offering specialized services such as medical equipment, compression stocking fittings, diabetic shoes fitting with shoe selection on site, vaccinations throughout the year and medical compounding (our compounding lab is located inside TLC called Custom Prescription Compounders, LLC). Our compounding pharmacist Zoom H. Heaton is also board certified in Anti-aging, Metabolic and Functional medicine. She works with patients needing help with various medical needs such as bio-identical hormone management, adrenal and thyroid issues, autoimmune conditions, weight management, pain management compounding, nutritional guidance using specialized testing and much much more. If you feel that your health needs a change for the better, call us at 803.648.7800 extension 200 and make an appointment. The first 15 minutes of your consultation with Zoom is free.
Picture of Zoom H. Heaton

Zoom H. Heaton

TLC Medical Centre pharmacy is a traditional pharmacy offering specialized services such as medical equipment, compression stocking fittings, diabetic shoes fitting with shoe selection on site, vaccinations throughout the year and medical compounding (our compounding lab is located inside TLC called Custom Prescription Compounders, LLC). Our compounding pharmacist Zoom H. Heaton is also board certified in Anti-aging, Metabolic and Functional medicine. She works with patients needing help with various medical needs such as bio-identical hormone management, adrenal and thyroid issues, autoimmune conditions, weight management, pain management compounding, nutritional guidance using specialized testing and much much more. If you feel that your health needs a change for the better, call us at 803.648.7800 extension 200 and make an appointment. The first 15 minutes of your consultation with Zoom is free.

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