The pituitary is a smaller gland that attaches to the bottom of the brain, behind the nose. It is in an area called the pituitary fossa/sella turicica. This gland is referred to as the master gland because it controls the production and regulation of hormones in the body.
The pituitary gland is similar to a thermostat you would have in your house. The thermostat is always taking the temperature of the house and making sure that the heat is constant and steady. This is how the pituitary gland works. It is always checking to make sure everything is functioning at the right levels to keep an ideal environment.
The pituitary gland job is to do the following:
- Growth and development
- Functioning of organs
- Functioning of glands
PITUITARY ANATOMY AND FUNCTIONS
The pituitary is made up of the anterior pituitary gland and the posterior pituitary gland. The two parts each have different cells that regulate and release different hormones. The anterior pituitary is made of the same tissue as the pharynx and the posterior pituitary is made up of an out-puching of the brain that is an extension of the hypothalamus. The neuroendocrine system is made up of the hypothalamus and the pituitary. The anterior pituitary makes up around 80% of the pituitary gland size and is separated into an anterior lobe and an intermediate zone. The anterior lobe has the job of producing many of the hormones that get sent into the bloodstream. The posterior pituitary gland is developed very early on in life and does not make any hormones. It contains the neurons that come from the hypothalamus. These neurons make some hormones including vasopressin and oxytocin which are brought down the pituitary stalk and to the posterior pituitary. Here they get stored to be released later on into the bloodstream. The pituitary and the hypothalamus have a relationship to control the functions of the body each day and also have a part in growth, reproduction, and development. Two types of hormones are secreted by the hypothalamus that control the secretion of different hormones that are released from the anterior pituitary. The pituitary gland does its job by letting out signaling hormones that control the activities of other organs.
The pituitary produces these hormones:
- Adrenocorticotropic hormone (ACTH): ACTH makes the adrenal glands release cortisol and aldosterone which regulate carbohydrate and protein metabolism as well as the levels of water and sodium
- Growth hormone (GH): this mainly works to regulate growth as well as the metabolic system
- Luteinizing hormone (LH) and Follicle - stimulating hormone (FSH): Controlsec hormones and regulate the menstruation cycle in women
- Melanocyte-stimulating hormone (MSH): Controls the production of melanin through melanocytes in the skin. If melanin production increases then the skin may tan.
- Prolactin (PRL): This has a job of stimulating the production of breast milk
- Thyroid-stimulating hormone (TSH) : This regulates the thyroid gland by telling it to release thyroid hormones. Thyroid hormones control the metabolism and function in growth and maturing. They affect most of the organs in the body.
- Vasopressin/Antidiuretic hormone(ADH): ADH works to increase the retention of water.
The fourth most common brain tumor is a pituitary adenomas. Most of these are benign and do not grow fast. Adenomas are the most typical disease that affects the pituitary gland. They often affect the ages of 30-40 years old but also may occur in children. The majority of these tumors can be treated. Functioning adenomas are tumors that produce hormones. Nonfunctioning adenomas.
Microadenomas are less than 10 millimeters in size and can secrete anterior pituitary hormones. Adenomas that are not as large in size and are functional can usually be diagnosed early because there will be more obvious symptoms present due to higher hormone levels. Around half of pituitary adenomas are caught when they are less than 5 millimeters in size. Macroadenomas are bigger than 10 millimeters in size and do not typically secrete hormones. They can cause symptoms that appear due to compressed brain or nerve structures.
Many of the symptoms from a pituitary tumor can be caused from endocrine dysfunction. This includes excess growth hormones or low production of thyroid hormones. Having abnormal hormone levels can affect the menstrual cycle, fertility, ability to withstand heat or cold, and more.
Pituitary tumors can put pressure on important brain structures as they grow bigger. They will often put pressure on the optic nerves which can lead to vision loss over time. Vision will usually deteriorate on both sides of the peripheral vision.
Multiple of the following symptoms may be signs of a pituitary tumor:
- Vision issues
- Headaches near the forehead
- Loss of smell
- Sexual dysfunction
- Growing issues
- Weight gain or weight loss without reason
- Bruising easily
- Aching in the joints
- Carpal tunnel syndrome
- Early menopause
- Weakness in the muscles
If a patient suspects a pituitary tumor, they should meet with a physical who can perform an examination and vision tests. Hormone tests of blood and urine as well as an MRI should be taken.
Early intervention provides the best chance for cure or control of a pituitary tumor and its side effects. There are three types of treatment used for pituitary tumors: surgical removal of the tumor, radiation therapy using high-dose x-rays to kill tumor cells and medication therapy to shrink or eradicate the tumor.
To have the best control over treatment, the earlier the tumor is diagnosed the better. To treat a pituitary tumor there are multiple options for treatment including surgery, radiation therapy, and high dose x rays to harm tumor cells.
One surgical technique would be to access the tumor using a microsurgical or endoscopic approach through the nasal cavity. This is called a transsphenoidal approach. The surgery can be assisted with the guidance of a computer using a minimally invasive approach. This type of surgery is often used for function adenomas and some macroadenomas. Prolactinomas need a certain dopamine agonist medication with surgery to be treated. Since transsphenoidal surgery is a minimally invasive procedure, there are usually little side effects as well as a quick recovery time. Patients could possibly leave the hospital two to three days post operation. A transcranial approach or a craniotomy is not typically to treat this condition.This approach is used on certain cases that usually involve very aggressive and large tumors.
High energy x-rays are used during radiation therapy to attack tumor cells. This type of treatment is beneficial in slowing and even stopping the growth of the tumor. The tumor can begin to shrink over time. If the tumor cannot be treated with medication or surgery this may be used.
Three main types of radiation used:
Standard External Beam Radiotherapy
Photons are created by a linear accelerator to form standard external beam radiotherapy. This therapy will usually be divided into a treatment a day, five days of the week for four or five weeks.
Proton Beam treatment
Protons are used during proton beam treatment to control the tumor. This can target more specific areas that photons as well as be given in higher dosages. Because of the higher dosages, there may be more risk to damage surrounding tissues.
Stereotactic radiosurgery is a combination of standard external beam radiotherapy with a radiation technique that goes through many ports. This treatment usually is less damaging to surrounding tissues and can be treated in less sessions.
The most common secreting pituitary adenoma is a prolactinomas. Medical therapy is usually the first path of treatment. Around 80% of patients have levels of prolactin restored to normal with the treatment of dopamine agonist therapy. Bromocriptine and cabergoline are the agents used the most often. With the size of the tumor decreasing, vision may begin to improve, headaches may wear off, and menstruation may begin again in women.
Cabergoline has the least amount of side effects as is used the most often. This required a dose to be taken two times of the week. Bromocriptine needs one dose a day to be taken and has side effects that include gastrointestinal upset and dizziness or nausea with fast movements.
Dopamine agonist therapy is often used for patients with small adenomas. This will be tried for multiple months. After this is tested, surgery could be considered an option. This should be done within a year of the start of doing medication therapy.
Here are some medications that are used in the treatment of adenmoas:
Growth hormone-secreting tumors (Acromegaly/Gigantism):
- Octreotide (Sandostatin)
- Lanreotide (Somatuline Depot)
- Cabergoline or bromocriptine
- Pegvisomant (Somavert)
ACTH- Secreting tumors (Cushing's syndrome/disease):
- Ketoconazole (Nizoral)
- Mitotane (Lysodren)
- Metyrapone (Metopirone)
- Mifepristone (Korlym)