Body-energy and Thyroid gland: As per Hindu mythology, during ocean churning (Samudra Manthan) at first deadly poison (Hala-hal Visha) emerged the same was consumed by Lord Shiva and kept in his throat. His wife Parvati (incarnation of Shakti) stopped Him to swallow it further. So, his throat turned blue. That is the reason, Lord Shiva is called ‘Neel-kantha’ i.e. having blue throat. Shakti (consort of Shiva) is also called energy and made her presence there and started utilizing this in the form of hormones to convert food into energy.
Nutrients, absorbed from the food we take, form body essentials like blood, flesh, muscles, fat etc. But all these body essentials need energy to be able to perform for the body activities. It is the thyroid gland that helps in converting food constituents into energy.
Location of thyroid gland and Parathyroid Gland: The thyroid gland is located on the front surface of the trachea. The function of the thyroid gland is to take iodine, found in many foods. Thyroid cells are the only cells in the body which can absorb the most important micro-nutrient iodine. Iodine forms 0.1% of mass of the body. Thyroid gland has two lobes. Iodine is trapped in the thyroid gland (Neck) and convert it into thyroid hormones. Iodine compounds are mostly of blue colour.
There are four parathyroid glands that are embedded in the thyroid gland. The parathyroid gland secretes a hormone called parathormone which helps to regulate calcium and phosphate levels in the blood.
Working of Thyroid hormones: Thyroid cells combine iodine and the amino acid tyrosine to make triiodothyronine (T3) and thyroxine which can sometimes be referred to as tetraiodothyronine (T4). T3 and T4 are then released into the blood stream and are transported throughout the body (to every cell) where they control metabolism (conversion of oxygen and calories to energy). T4 (inactive hormone) is the primary hormone produced by the thyroid. T4 is then converted to T3 (active) to be used in a properly functioning metabolism. Thyroxine (T4) is responsible for your metabolism, mood, and body temperature, among other things. T3 can also be made in other tissues within the body by converting T4. Only 15% T3 is coming directly from the thyroid gland while 85% T3 is converted from T3.
Both these hormones should be released in balanced way in proper quantity in order to be heathy, otherwise it will act as poison for the body. The deficiency of iodine in the diet can cause a deficiency of thyroxin hormone in the body. This causes a disease called a goitre.
Functioning of total system: The hypothalamus in the brain acts as a kind of internal thermostat, sending out signals through pituitary gland to thyroid gland to produce hormones to control heat or cool the body down and to decrease or increase metabolism.
Hormonal output from the thyroid is regulated by thyroid-stimulating hormone (TSH) produced by the Thyrotropes, special cells in the anterior pituitary that release thyroid-stimulating hormone (TSH). Production of TSH is regulated by thyrotropin-releasing hormone (TRH) produced by the hypothalamus. The pituitary constantly monitors our thyroid hormone levels, and if it senses the slightest excess of thyroid hormone in blood, it stops producing TSH. Lower thyroid hormones increase TSH production and higher thyroid hormone levels decrease the TSH level. Consequently, a low blood TSH strongly suggests that the thyroid is overproducing hormone on its own.
The thyroid and thyrotropes form a negative feedback loop: TSH production is suppressed when the T4 levels are high. The TSH production itself is modulated by thyrotropin-releasing hormone (TRH), which is produced by the hypothalamus and secreted at an increased rate in situations such as cold exposure (to stimulate thermogenesis).
Effect of stress on thyroid hormones: When one is chronically stressed, hypothalamus release CRH to pituitary gland. Pituitary gland sends signal through ACTH to adrenal glands. Adrenal fatigue may kick in, triggering the adrenal glands to release cortisol hormones as a way of coping. Thus, there is a relationship between adrenal health and thyroid health. Too high levels of cortisol not only impair the body’s ability to create the T4 hormone, it also suppresses the conversion of T4 to T3 which then leads to a dysfunctional metabolism. This chronic stress can worsen thyroid issues, leading to imbalanced hormone levels. When chronically stressed, one might notice slowed metabolism and weight gain — and stress may even further lower levels of T3 and T4. It can also affect the conversion of T4 into T3.
While Hypothalamus Stimulates the production of thyroid hormones to boost the metabolism, TSH production is blunted by somatostatin (SRIH), rising levels of glucocorticoids and sex hormones (oestrogen and testosterone), and excessively high blood iodide concentration. Somatostatin is known by the name of growth hormone inhibiting hormone, it is produced in the gastrointestinal (GI) tract, pancreas, hypothalamus, and central nervous system. Too much somatostatin results in extreme reduction in secretion of many endocrine hormones. An example of this is suppression of insulin secretion from the pancreas leading to raised blood glucose levels (diabetes). As somatostatin inhibits many functions of the gastrointestinal tract, its overproduction may also result in the formation of gallstones, intolerance to fat in the diet and diarrhoea.
Thyroid gland and integration of body functions: The major areas of control and integration include responses to stress and injury, growth and development, absorption of nutrients, energy metabolism, water and electrolyte balance, reproduction, birth, and lactation. These glands include the pituitary gland, the pineal gland, the hypothalamus, the thyroid gland, the parathyroid glands, the thymus, the adrenal glands, the ovaries (in females) or testes (in males), and the pancreas. These hormones are released into the blood stream. Tissue response to hormones usually occurs after a lag time of seconds or days. Once started the responses tend to be much more prolonged than those that are induced by the nervous system.
The hormones testosterone and oestrogen play a leading role in one’s metabolism. Some other hormones that also play a critical role in successful weight management include cortisol, insulin, progesterone, and thyroid hormone triiodothyronine (T3).
Major roles of thyroid gland: The thyroid gland secretes hormones that affect almost every function in the body including brain functions and heart functions; such as regulating body temperature, the rate of heartbeat and respiration, metabolism and energy levels regulation in the body.
Major roles of the thyroid gland can be described as follows.
- Maintaining body temperature: Thyroid hormone primarily converts triglycerides and protein breakdown products into heat. One of the hormones, thyroxine is used by mitochondria to produce heat to maintain body at temperature of 370C.
- Control of body energy and sensitivity for other hormones: The thyroid gland controls how quickly the body uses energy, makes proteins, and controls how sensitive the body is to other hormones. The thyroid hormones instruct the cells to increase the rate at which they convert oxygen and nutrients into energy and heat for the body’s use.
- Growth and development: Thyrotropic Hormone plays an important role in growth and development. Thyrotropin, also called thyroid-stimulating hormone (TSH), is produced by cells called thyrotrophs in the anterior pituitary gland. Growth (Upachaya) is a function of Kapha therefore function of thyrotrophic hormone is similar to Kapha -Dosha function. This hormone influences the activity of thyroid gland and according to Ayurveda, all activities are mediated only by Vata Dosha.
- Growth rate in children: Thyroid hormones increase growth rate in children, stimulate mental activity, and step up the activities of other endocrine glands. Adequate thyroid hormone is crucial for brain development during infancy and childhood.
- Cholesterol metabolism: Thyroid and cholesterol are related with each other. Cholesterol is in plasma membrane of every cell. Liver makes cholesterol. Liver also removes cholesterol returned after circulation, with the help of thyroid hormones. LDL returned after circulation should not be oxidised. Cholesterol metabolism is affected by thyroid hormones. In case of low thyroid hormones, cholesterol problems come.
- Calcium homeostasis: The thyroid also produces calcitonin, which plays a role in calcium homeostasis by regulating calcium function along with the parathyroid gland.
Thus, this small gland controls the functioning of all organs including heart, musculoskeletal system, and brain. The gland help bone cells to add calcium to bone. These hormones from thyroid are important right from foetal life to old age; controlling everything.