The thyroid gland releases triiodothyronine (T3) and thyroxine (T4). These hormones play an important role in regulation of your weight, energy levels, internal temperature, skin, hair, nail growth, metabolism and is an important part of the endocrine system.
Although it gets less attention than thyroid hormones, the parathyroid hormone is still important in the body. Parathyroid hormone is connected to blood calcium levels in the bones, intestines and kidneys. Parathyroid hormone comes from four parathyroid glands in the neck, just behind the thyroid. These glands receive feedback from blood calcium levels to determine when they need to secrete the hormone. The hormone plays a role in regulating blood calcium levels, helping the body maintain adequate calcium stores in the bloodstream to protect bone health.
What is T4?
Thyroxine (T4) is produced by the thyroid gland under regulation from the hypothalamus and pituitary gland. The feedback loop signals to the hypothalamus in to release thyrotropin-releasing hormone, which then stimulates the pituitary gland to release the thyroid stimulating hormone.
What is T3?
T3 is a second thyroid hormone that is produced by the thyroid gland, but also in other tissues through deiodination (enzymatic conversion) of T4. T3 helps maintain muscle control, brain function and development, heart and digestive functions. It also plays a role in the body’s metabolic rate and the maintenance of bone health.
Problems Associated with T3 and T4?
Having too much T3 in the bloodstream is referred to as thyrotoxicosis. This condition often results from overactivity in the thyroid gland, or hyperthyroidism. Hyperthyroidism occurs in conditions such as Graves’ disease, inflammation of the thyroid or a benign tumor. Signs of thyrotoxicosis include weight loss, increased appetite, palpitations, irregular menstrual cycle, tiredness, irritability, and hair thinning. Hyperthyroidism can also occur when supplements with T3 are ingested.
Hypothyroidism is a condition that occurs if the thyroid gland does not produce enough of the thyroid hormone. This may be due to autoimmune conditions, such as Hashimoto’s thyroiditis or certain medications. Hypothyroidism can also occur in pituitary dysfunction, such as pituitary tumors or inflammation.
Hypothyroidism tends to run in families and more common in adults, as well as women. Symptoms may include tiredness, mental depression, feeling cold, weight gain, dry skin, constipation, and menstrual irregularities.
Parathyroid hormone helps prevent low calcium levels by acting on the bones, intestine, and kidneys. In the bones, the hormone triggers the release of calcium stores from the bones to the blood. This can lead to bone destruction. In the intestines, parathyroid hormone helps with vitamin D metabolism. This, in turn, allows the body to absorb more of the calcium it digests from food. In the kidneys the hormone stops the release of calcium through the urine, while also increasing vitamin D production.
Because the function of parathyroid hormone directly impacts blood calcium levels, improper balance of parathyroid hormone can cause an imbalance of calcium levels in the blood.
Having too much of the hormone can cause a condition known as hypercalcaemia, which increases blood calcium levels. This does not cause obvious symptoms in mild cases, but if levels rise too high, it can cause digestive upset, constipation, depression, lethargy, weakness, joint pain, and excessive thirst. Hypercalcaemia is typically discovered during routine blood testing. Too little parathyroid hormone causes a rare condition called hypoparathyroidism, which leads to low blood calcium levels. This is fairly easy to treat using vitamin D and oral calcium tablets, once it is discovered.
Because parathyroid hormone problems rarely cause symptoms at the beginning of the condition, be sure to ask your doctor about parathyroid hormone levels when having routine blood work done.