Thyroid Physiology

The Influences of Thyroid Hormones on Physiological and Metabolic Function

 Bone:  Deficiency of thyroid hormones lead to a decrease in bone development and an abnormal architecture of the bone that is created.  Generally, a functionally low (which means low but not flagged as of yet) serum calcium is noted in hypothyroidism.  Elevated thyroid hormones causes an increased serum calcium, as it pulls calcium from the bone, leading to increased risk of pathological fractures of the spine and weight bearing joints.

 GastroIntestinal Function:  Transit time is affected directly by thyroid hormones as is absorption of nutrients. 

 Male Hormones:  Hypothyroidism has been linked to diminished libido and impotence.  Although this condition is more rare in men, it must be considered in treating these conditions.

 Liver and Gallbladder Function:  Low thyroid function caused decreased liver clearance and gall bladder congestion through thickening of the bile, often also associated with an elevation of cholesterol.  Unfortunately, also often treated with cholesterol lowering drugs while the thyroid function is the cause of the elevated cholesterol. 

 Body Composition:  As you may know all too well, low thyroid function causes an inability to lose weight.  This is caused by a slowed conversion of glucose and fat into energy, and altering the way Human Growth Hormone (HGH) is metabolized in the body. 

 Blood Sugar Regulation:  Low thyroid slows the insulin response to glucose following eating carbohydrates or sugar and it also slows glucose uptake into cells and tissues, and slows absorption of glucose from the intestinal tract.  In other words, your entire energy production system is slowed.  It is quite confounding to your body and brain, in that the glucose is in the blood, but the tissues are not able to absorb it.  This really confuses the pituitary gland and adrenal glands, resulting in a “stress physiology,” even if life is good. 

 Cholesterol:  As mentioned earlier, low thyroid increases your cholesterol and triglycerides, so your doctor tells you your diet is poor.  You become even more strict in your diet, and the tissue starvation (low glucose, low energy) gets worse, which makes the stress physiology worse, which makes your cholesterol higher, which prompts your doctor to put you on cholesterol medication, which interferes with energy production, which further stresses your physiology…whew!  You are frustrated!

 Depression:  Low thyroid impairs the production of stimulating neurotransmitters, which are the chemicals that antidepressants work on.  Low stimulating neurotransmitters leaves you feeling depressed.

 Female Hormones:  Low thyroid changes the way estrogen is metabolized in the body, shifting toward a estrogen metabolite that has been proven to increase the risk of breast cancer. 

 Stress:  Low thyroid slows the elimination of the stress hormone cortisol, which leaves you feeling stressed out, not because of “stress,” but because the stress hormone can’t be removed efficiently. 

 Detoxification:  Low thyroid slows an enzyme critical for metabolic biotransformation, or detoxification, the process by which the body binds and removes all environmental chemicals, and normal byproducts of metabolism, including hormones.  “Toxicity” further slows your metabolism, and leads to headaches and other toxic symptoms.

 Digestion:  Low thyroid reduces the release of gastrin, which determines the output of hydrochloric acid in the stomach, leading to poor protein digestion, sour stomach, and GERD.

 Thermoregulation:  Regulation of body temperature is affected by low thyroid, resulting in hot flashes and night sweats, which is especially prominent in perimenopausal women.  This is often blamed on estrogen dropping, but may be directly caused by low thyroid. 

 PMS and Infertility:  Low thyroid affects the progesterone receptors, making them less sensitive to progesterone, which feels like low progesterone, although the progesterone levels may be normal.  Since the activity of progesterone is diminished, the health of the uterus is insufficient for implantation in the second half of the female cycle, leading to difficulties getting pregnant and PMS.  Low thyroid also reduces sex hormone binding proteins, leading to an increase in estrogen activity. 

 Anemia:  Low thyroid, as mentioned affects protein metabolism, which then lowers the red blood cell mass, which carries oxygen to tissues for metabolism of energy.  Yes, another mechanism for feeling lousy. 

 Homocysteine:  Low thyroid slows a process called methylation, often evidenced by elevated serum levels of homocysteine.  Elevated homocysteine in the blood has been proven as a risk factor for cardiovascular disease, alzheimers and other neurodegenerative disorders, and cervical dysplasia. 

 As you can see, living with low thyroid has far reaching effects on your health and function.  There are as many as 23 published mechanisms for thyroid function to be impaired.