WHAT IS THE PITUITARY GLAND?
Pituitary gland is an organ with the size of a hazelnut, located in a small space in the skull under the brain (skull base), connected with the brain via the pituitary stalk but separated from it (under the brain’s control) and controls the hormonal system of the whole body.
Pituitary gland has three major parts: Anterior lobe (adenohypophysis), posterior lobe (neurohypophysis) and the intermediate lobe. All three lobes are connected and are under the control of hypothalamus.
Anterior lobe (Adenohypophysis)
Anterior lobe synthesizes and secretes hormones. These are:
- Adrenocorticotropic hormone (ACTH)
- Thyroid stimulating hormone (TSH)
- Growth hormone, or “somatotropin” (STH)
- Prolactin (PRL), or ” luteotropic hormone” (LTH)
- Melanocyte stimulating hormone (MSH)
Gonadal hormones (gonadotropins):
- Luteinizing hormone (LH)
- Follicle stimulating hormone (FSH)
Posterior Lobe (Neurohypophysis)
Posterior lobe does not synthetize hormones. Hormones secreted from the posterior lobe are produced in the hypothalamus and are stored here. These are:
- Vasopressin, or ” antidiuretic hormone ” (ADH)
The pituitary has an intermediate lobe in most living beings. In adult humans, this is a very thin layer of cells between the anterior and posterior lobes. This lobe produces MSH, although not very certain.
Functions of the pituitary hormones are as follows:
- Blood pressure regulation
- Controls the pregnancy and helps labor by making the uterus muscle contract
- Breast milk production and secretion
- Sexual organ function in males and females
- Thyroid gland functions
- Converting food into energy (metabolism)
- Regulation of the body’s water balance
- Regulation of water reabsorption in kidneys (with ADH)
- Regulation of body temperature
Pituitary tumors usually come up as benign pituitary adenomas. Very rarely, malignant pituitary carcinomas can be seen. Signs and symptoms can be classified into four major groups: 1- Excessive hormone production 2- Preventing hormone production with compression 3- Compressing neighboring brain structures with overgrowth (blindness) 4- Bleeding into tumor and causing an emergency situation (pituitary apoplexy)
EXCESSIVE HORMONE PRODUCTION
Pituitary adenomas cause signs and symptoms depending on the cell type of its origin, as stated above.
The most common type is prolactinoma, characterized by excessive prolactin secretion. This disease causes milky discharge from breasts in both men and women; irregular menstrual periods and not being able to get pregnant in women; erectile dysfunction and reduced sex drive in men, enlarged breasts and osteoporosis.
Tumors secreting growth hormone cause a clinical syndrome “called acromegaly”. It can cause enlarged hands and feet (patient’s shoe size grows), coarsened facial features, growing nose, insulin intolerance (up to diabetes) and heart dysfunction.
Excessive secretion of adrenocorticotropic hormone (ACTH) causes a special condition called “Cushing’s disease”. Excess cortisol levels in the body causes signs and symptoms including weight gain characterized with trunkal fat, thickening nest, moon face, increase in body hair, stretch marks on abdomen, hypertension, diabetes, osteoporosis, muscle weakness and psychological imbalance.
Excessive thyroid stimulating hormone (TSH) secretion causes signs and symptoms of hyperthyroidism, including heat intolerance, shaky hands, arrhythmias, weight loss and irritability. Excess FSH and LH levels are characterized with menstrual irregularities and infertility in women.
MASS EFFECT OF THE TUMOR AND VISION LOSS DUE TO PITUITARY TUMORS
Extremely large tumors can cause visual disturbances that can lead to blindness either by preventing the pituitary’s hormone secretion or by compressing the neighboring visual nerves. Rarely, a sudden bleeding into the tumor occurs and causes a clinical scenario called “pituitary apoplexy” characterized by vomiting, sudden loss of consciousness, coma and sudden blindness. Urgent surgical treatment is life-saving in this situation.
TREATMENT IN PITUITARY TUMORS
Treatment in pituitary tumors can be categorized into three groups: 1- Medical treatment 2- Surgical treatment and 3- Surgical treatment in combination with gamma-knife
One of the most important factors driving the treatment decision is the size of the tumor. Tumors smaller than 1 cm are called microadenomas whereas larger than 1 cm are called macroadenomas. If a tumor is prolactinoma and microadenoma, it is generally cured with medical treatment. If a tumor is macroadenoma or causes a clinical condition like Cushing’s syndrome or acromegaly regardless of its size it requires surgical treatment. Sometimes macroadenomas invade an anatomical region called cavernous sinuses adjacent to both sides of the pituitary. This region cannot be totally cleaned with surgery, so gamma-knife radiation therapy is used as supplementary treatment. It should be highlighted that gamma-knife is not a treatment option by itself; it can only be used alongside with surgical treatment.
Pituitary surgery (pituitary tumor operations) are performed through the nose and the physician removes the tumor without an incision to the face or head either with a microscope or an endoscope. Patients can experience discomfort because of nasal tampons for two days after the surgery. In excessive hormone-secreting tumors, patients are dramatically relieved in a short time because the hormonal imbalance is over. Especially patients with Cushing’s disease experience dramatic recovery including their image and they can go back to their normal lives. Rarely, pituitary tumors are operated with open head surgery. These operations are performed safely by experienced brain surgeons.