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Structure, Functions and Disorders of Pituitary Gland, Thyroid Gland, Parathyroid Gland

Anterior lobe, Growth hormone, Thyroid stimulating hormone, Adrenocorticotropic hormone, Follicle stimulating hormone, Luteinizing hormone, Prolactin.

Pituitary gland

Your endocrine system includes the pituitary gland. It is responsible for secreting hormones into your body. Such hormones have an effect on many other organs and glands, such as:
  • Adrenal glands
  • Thyroid
  • Reproductive organs
The pituitary gland is sometimes referred to as the master gland due to its involvement in so many processes.

Structure and functions

Pituitary glands are small and oval-shaped and are located in the brain. Near the underside of the nose, it is located behind the pituitary gland. The stalk-like structure connects the cortex to the hypothalamus. Your hypothalamus is a small region of the brain. It helps your body balance its functions. The pituitary gland releases hormones that regulate the functions of your body. The anterior and posterior lobes of the pituitary gland are separated by a ligament.

Anterior lobe

There are several different types of cells in the anterior lobe of the pituitary gland, and they produce and release a wide range of hormones, including:

Growth hormone - Growth and development are controlled by growth hormone. Almost every tissue in the body can be stimulated by it. The primary targets are the muscles and bones.

Thyroid stimulating hormone - The release of thyroid hormones is triggered by this hormone. Thyroid hormones are essential to the metabolic process.

Adrenocorticotropic hormone - When your adrenal glands are stimulated by this hormone, cortisol and other hormones are released.

Follicle stimulating hormone - A female's oestrogen secretion and the production of eggs is affected by follicle-stimulating hormone. Follicle-stimulating hormone is also vital in producing sperm in men.

Luteinizing hormone - Women make oestrogen while men make testosterone from luteinizing hormone.

Prolactin - Milk is produced by women who are breastfeeding through prolactin.

Endorphins - Endorphins are thought to be linked to the brain's "pleasure centers" and have pain-relieving properties.

Enkephalins -
The pain-relieving effects of enkephalins are similar to those of endorphins.

Beta- melanocytes stimulating hormones - Exposure to ultraviolet radiation stimulates the production of this hormone, which leads to increased skin pigmentation.

Posterior lobe

Pituitary hormones are also secreted by the posterior lobe of the gland. This hormone is produced in the posterior lobe of the hypothalamus, where it is stored until it is released. The posterior lobe stores the following hormones:

Vasopressin - Known also as antidiuretic hormone. It prevents dehydration and conserves water in your body.

Oxytocin - Breast milk is stimulated by this hormone. This hormone is also responsible for uterine contractions during labor.

Disorders

There are several conditions that can affect the pituitary gland. The most common condition is tumors of the pituitary gland. Hormone production may be affected by this. Among the disorders of the pituitary gland are:

Pituitary tumors - Most pituitary tumors do not cause cancer. The production of hormones, however, is affected. If they press against other brain areas, you may experience vision problems or headaches.

Hyperprolactinaemia - A high concentration of prolactin is present in your blood in this condition. A lack of sex drive and infertility can result.

Traumatic brain injury - A sudden blow to the head causes the brain to be damaged. When your pituitary gland is injured, it can sometimes cause memory loss, behaviour issues, or communication difficulties.

Hypopituitarism - One or more of your pituitary gland's hormones are produced very little or not at all under this condition. It may impact your reproductive system or growth.

Acromegaly - The pituitary gland overproduces growth hormone in this condition. Excessive growth between your fingers and toes may occur. Pituitary tumours often cause it.

Thyroid gland

Structure

Located on the anterior side of the neck, in front of the trachea, the thyroid gland is shaped like the winged claw of a butterfly. This gland weighs about 25 grams and consists of two lobes on either side of the trachea. The lobes are cone-shaped and measure 5cm in length and 3cm in width. This isthmus, a median mass of tissue connecting the two lobes, lies between them. A gland's inner structure is composed of hollow spherical follicles scattered throughout the structure. A cuboidal epithelial cell called a follicular cell forms the walls of these follicles. Thyroglobulin, a glycoprotein present in these cells, secretes thyroid hormones. Colloid is an amber-colored, sticky liquid that is released by the hormone. Parafollicular cells also form part of the thyroid gland, which produces calcitonin in addition to follicular cells. Unlike connective tissue, the parafollicular cells do not form a separate mass from the follicular epithelium. The thyroid gland receives arterial blood from the superior and inferior thyroid arteries.

Functions

There are several functions performed by the thyroid gland:
  • Thyroid hormones, essential for metabolism and growth, are the thyroid gland's most important function.
  • It influences glucose, fat, and protein metabolism in the body by regulating the basal metabolic rate.
  • Several hormonal compounds contain iodine atoms, so they also participate in the metabolism of iodine in the body.
  • Calcitonin produced by the C cells of the thyroid gland is responsible for controlling the calcium ions in the blood.
  • There are a number of target organs of the body that are boosted by thyroid hormone, such as the brain and kidneys.

Disorders

Generally, thyroid disorders and diseases are caused by excessive or insufficient hormone secretion. Thyroid gland and its secretions are associated with the following disorders;

Grave's disease

Grave's disease is thyroiditis caused by the overproduction of thyroid hormones. This condition can affect anyone, but is more prevalent among people between 30 and 50 years old, and is more likely to affect women than men. Grave's disease is a thyroid disorder characterized by abnormal antibodies directed against thyroid cells. Antibodies that mimic pituitary hormone production in the thyroid cause the gland to produce thyroid-stimulating hormone. A person with this condition is likely to experience nervousness, sweating, weight loss, and elevated metabolism.

Simple goiter

The cause of simple goiter is hypothyroidism caused by enlargement of the thyroid gland, which results in low thyroid hormone production. Generally, goiters are caused by enlargement of the thyroid gland due to an excess of thyroid tissue. This condition is caused by persistent iodine deficiency, which leads to the body not producing adequate amounts of T3 and T4. When the gland grows too large, adjacent tissue such as the esophagus and nerves can be damaged.

Cretinism

Cretinine is a condition in which thyroid hormone is not properly secreted by the thyroid gland. Mental retardation and a disproportionately large body are the main symptoms of the condition. Depending on how active the individual is and his or her age, the condition has varying effects, but children often suffer more than adults. Those who suffer from ceretinism may have a genetic thyroid deficiency or be lacking in iodine due to maternal factors.

Thyroid tumors

Cancerous thyroid tumors are extremely rare, while benign tumors, including simple adenomas, are somewhat more common. An older adult, on the other hand, might develop a malignant tumor. There is the possibility that even benign tumors will produce excessive amounts of hormones, causing hyperthyroidism.

Parathyroid gland

Structure

A nodular structure developed from endodermal tissue, the parathyroid glands are located on the surface of the thyroid gland. Each of the glands weighs an average of 50 grams, but the size of the glands varies from person to person. The glands are encased inside finely woven connective tissues that enclose spherical cells arranged in columns surrounded by sinusoids filled with blood. The parathyroid glands consist of two types of cells: chief cells and oxyphil cells. Chief cells play the dual function of synthesizing and secreting parathyroid hormones from the parathyroid gland. Regulation of hormone synthesis and release is dependent on serum calcium levels. A calcium-sensing receptor (CaSR) can detect low blood calcium levels by responding to the surface of the chief cells. Parathyroid glands also contain oxyphil cells, also known as oxyntic cells, but they do not function as endocrine cells. With age, the parathyroid gland produces more oxyphil cells.

Functions

Parathyroid gland functions include the following;
  • Parathyroid hormone is essential for maintaining calcium homeostasis in the body, and it is produced and released by the parathyroid gland.
  • Inhibiting osteoblastic activity and stimulating osteoclastic activity leads to calcium breakdown and release from the blood stream when parathormone is released from the gland.
  • In addition, the parathormone regulates the calcium transporter in the nephrons, which are responsible for calcium reabsorption.
  • Increasing vitamin D synthesis by the parathyroid gland increases calcium and phosphate reabsorption from the gut, so it isn't directly active in the digestive tract.

Disorders

Among the parathyroid gland's disorders and diseases, we have;

Primary hyperparathyroidism

Approximately 2% of people over the age of 55 suffer from primary hyperparathyroidism, which is more prevalent in women. Several factors contribute to it, including adenoma and hypertrophy of the glands. As a result of hypersecretion of the hormone, hypercalcemia occurs and bones become weak. An increase in blood calcium levels can be used to diagnose primary hyperparathyroidism.

Secondary hyperparathyroidism

Low calcium levels cause secondary hyperparathyroidism, which is characterized by adequate parathormone secretion. If the increased secretion causes hypercalcemia, it can result in primary hyperparathyroidism. Secondary hyperparathyroidism can also cause gastroesophageal reflux in addition to kidney stones and bone pain.

Hypoparathyroidism

A condition characterized by reduced parathyroid hormone production is hyperparathyroidism. In this condition, hypocalcaemia is present, as well as hyperphosphatemia and increased calcium ions. Several factors may cause it, including genetics, autoimmune diseases, or other conditions. Tetany, seizure and distorted bone microarchitecture are symptoms of chronic hypoparathyroidism.

Parathyroid carcinoma

In middle-aged, hyperparathyroid adults, a rare type of malignancy called parathyroid carcinoma causes this condition. Symptoms of renal colic, fractures, polyuria, and osteopenia can be caused by carcinomas of the kidney and bones. The parathyroid carcinoma can be surgically removed and the tissue analyzed for a definitive diagnosis.
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Ankur Choudhary is India's first professional pharmaceutical blogger, author and founder of pharmaguideline.com, a widely-read pharmaceutical blog since 2008. Sign-up for the free email updates for your daily dose of pharmaceutical tips.
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