Pituitary tumor, these days, is often an incidental finding on an MRI of CT scan of the brain done for some other medical reason. Let me first explain what is pituitary gland, what is its normal function, before I dive into the pituitary tumor.
What is Pituitary gland?
Pituitary gland is a small structure, the size of a pea, located in the under surface of the brain. A pituitary gland is essential for a person to live. It controls the function of most endocrine glands (hormone producing glands) in the body.
What are Pituitary Hormones?
The Pituitary gland controls the function of other endocrine glands by secreting several important hormones including:
1. TSH (thyroid stimulating hormone)
2. ACTH (adrenocorticotropic hormone)
3. FSH (Follicle stimulating hormone)
4. LH (luteinizing hormone)
5. GH (Growth hormone)
7. ADH (antidiuretic hormone)
These pituitary hormones, in turn, control the function of several endocrine organs (the target organs) in the body.
TSH regulates the production of Thyroid hormones (T4 and T3) by the thyroid gland.
ACTH regulates the production of Adrenal hormones (cortisol and sex hormones) by the adrenal glands.
LH and FSH regulate the production of Sex hormones and eggs by the ovaries in women and Sex hormones and sperm by the testes in men.
GH regulates growth during childhood and puberty and continues to regulate the health of bones and muscles in adults.
Prolactin regulates Lactation in women.
ADH regulates the urine concentrating ability of the kidneys.
The target organ hormones control the production of pituitary hormones through a negative feedback mechanism. For example, if thyroid hormones (T4 and T3) are low, the pituitary gland produces a large amount of TSH, whereas production of TSH is diminished in response to a high level of thyroid hormones (T4 and T3).
Pituitary hormone production is also controlled by a higher center in the brain called the hypothalamus, which in turn is influenced by the other areas in the brain, especially the limbic system, which is involved in regulating the emotions of a person. This explains how the emotional state of a person can influence the function of the endocrine organs. For example, women experiencing severe emotional trauma often stop having their menses.
A Pituitary tumor is benign in most patients, but rarely may be cancerous. When cancerous, it is usually the manifestation of a metastases from a distant site such as the lung, colon, breast, etc.
A Pituitary tumor is often discovered incidentally on a brain CT or MRI scan.
Pituitary tumors may be hormone producing tumors or non-hormone producing.
Symptoms of Pituitary Tumor
A Pituitary tumor may cause symptoms through one of the following mechanisms:
1. Symptoms of Pituitary Tumor due to pressure of the pituitary tumor on the surrounding structures in the brain.
Pressure of the pituitary tumor on the surrounding brain structures can give rise to defects in the visual field, double vision and severe headaches.
2. Due to overproduction of hormones by the pituitary tumor.
A pituitary tumor may produce one or more of the pituitary hormones. This type of pituitary tumors are called functional or hormone -producing tumor.
Prolactin producing tumor – Prolactinoma
Prolactin producing tumor is the most common type of pituitary tumor. It is called Prolactinoma.
High prolactin level in women can give rise to milk production, menstrual irregularities or infertility. High prolactin level in men can decrease testosterone level which in turn causes a decrease in libido, impotence and muscle weakness. High prolactin level is not always due to a pituitary tumor and can result from certain drugs, hypothyroidism, renal failure, breast manipulation, food, stress, etc.
Growth hormone producing tumor
Growth hormone producing tumor is rare. It can give rise to a disease state, known as Acromegaly.
ACTH (adrenocorticotropic hormone) producing tumor
ACTH (adrenocorticotropic hormone) producing tumor is rare and may give rise to a disease state, known as Cushing’s syndrome.
TSH producing tumor
TSH producing tumor is even rarer and can give rise to hyperthyroidism (overactive thyroid).
LH and FSH producing tumor
This type of pituitary tumor is rare. Itcan give rise to sexual symptoms in men as well as women.
3. Symptoms of Pituitary tumor due to underproduction of pituitary hormones:
Symptoms of a pituitary tumor may arise due to the local pressure effect of the tumor on the pituitary gland. Consequently, there may be under-production of the pituitary hormones. this condition is called Hypopituitarism.
What is Hypopituitarism
Underproduction of pituitary hormones is known as hypopituitarism, which can result from the pressure effect of the pituitary tumor on the pituitary gland or due to surgery and/or radiation therapy of a pituitary tumor.
Hypopituitarism usually manifests as fatigue and muscle weakness due to low thyroid hormones, low cortisol, low growth hormone and in men, low testosterone level as well.
Treatment of Pituitary tumor
Management of a pituitary tumor is complex and must be carried out in consultation with an endocrinologist.
Evaluation of a pituitary tumor includes:
- Is the pituitary tumor producing a hormone or not?
- Is the pituitary tumor causing any pressure effects on the surrounding brain structures?
- Is there evidence of hypopituitarism?
Prolactin producing tumors are effectively treated with medications. Surgery is only rarely indicated.
Other pituitary tumors generally require surgery and at times, radiation therapy as well.
Hypopituitarism is treated effectively by replacing the deficient hormones. treatment of hypopituitarism is life-long.