Hypopituitarism can involve one or more pituitary hormones. The term Multiple Pituitary Hormone Deficiency (MPHD) is sometimes used to describe the condition when the pituitary is not secreting two or more of the hormones it would usually produce. If all the hormones produced by the pituitary are affected this condition is known as panhypopituitarism. There are six important hormone groups produced by the pituitary gland which we consider when referring to hypopituitarism.
- Growth hormone, which is important for growth, but also has an important role in bone strength and well-being.
- The gonadotropins (luteinising hormone and follicle stimulating hormone) which stimulate the ovaries and testis to produce oestrogen and testosterone respectively, but are also important for fertility.
- The natural steroid, cortisol.
- Prolactin, the breast feeding hormone.
- Thyroid stimulating hormone which regulates release of thyroid hormones from the thyroid.
- Arginine vasopressin which acts on the kidneys to concentrate the urine and retain water.
There are a large number of causes of hypopituitarism. Most often it is caused by a benign (i.e. not cancerous) tumour of the pituitary gland.
Pituitary under activity may be caused by the direct pressure of the tumour mass on the normal pituitary, but also may result from surgery or radiotherapy used to treat the tumour.
Pituitary dysfunction following a traumatic brain injury may occur and is a serious consequence. We would therefore advise that you contact your GP if you have any concerns and experience some of the following symptoms: mild headaches, feeling sick, problems concentrating, poor memory, irritability, tiredness, problems sleeping, lack of appetite, sexual and fertility difficulties, depression, an increased thirst and excessive urinating.
Less frequently, hypopituitarism can be caused by tumours in the region surrounding the pituitary gland (i.e. craniopharyngioma, meningioma); cysts within the pituitary gland (i.e. Rathke’s cleft cyst); infections (such as meningitis) in or around the brain; inflammation of the pituitary gland (i.e. Hypophysitis, see below); severe blood loss; or by various rare diseases such as sarcoidosis (an illness which resembles tuberculosis).
Sheehan’s Syndrome is also known as postpartum hypopituitarism, or postpartum pituitary insufficiency and may occur in a woman who has severe uterine haemorrhage during childbirth. The resulting severe blood loss causes tissue death in her pituitary gland and leads to hypopituitarism following the birth. If a woman’s pituitary gland is starved of blood due to her bleeding severely during childbirth, the gland may lose its ability to function properly. Conditions that increase the risk of an obstetric haemorrhage include multiple pregnancies (twins or triplets) and abnormalities of the placenta. Blood tests would establish hormone levels and a scan to rule out other abnormalities of the pituitary such as a tumour.
Another cause of hypopituitarism that may be associated with pregnancy is lymphocytic hypophysitis. This is due to inflammation in the pituitary caused by immune cells. The reasons why this occurs is not understood. With modern obstetric practice the occurrence of hypopituitarism after childbirth, though uncommon, is more frequently due to this condition than Sheehan’s syndrome.
The symptoms of hypopituitarism relate to the loss of one or more of the hormones produced by the pituitary. Decrease in the production of only one hormone would lead to a number of symptoms, but would not result in all the symptomslisted. The specific symptoms an individual experiences would be dependent on which hormones are lost.
- excessive tiredness and decreased energy
- muscle weakness
- reduced body hair
- irregular periods (oligomenorrhoea) or loss of normal menstrual function (amenorrhoea) – females
- impotence – males
- reduced fertility
- decrease in sex drive
- weight gain or loss
- increased sensitivity to cold
- constipation or loose motions
- nausea and loss of appetite
- dry skin
- pale appearance
- low blood pressure and dizziness on standing (postural hypotension)Excessive urination and dry mouth (AVP Deficiency, formally(Diabetes Insipidus)
Once suspected the diagnosis of hypopituitarism is made from blood tests to measure the levels of the pituitary hormones themselves and/or the hormones produced by the glands they control (i.e thyroid, adrenal, gonads). Some hormones can be measured by a simple blood test, however, this often needs to be taken first thing in the morning as levels of several pituitary hormones vary significantly through the day (i.e. the natural steroid, cortisol and testosterone).
Other hormones, such as growth hormone, have very low levels and therefore require a test to stimulate release of the hormone so that it can be measured accurately. This is termed a stimulation test. There are a number of different stimulation tests that are used depending on which hormone is being examined. Where there is doubt over the level of cortisol on a simple blood test, a stimulation test may be required to confirm if an individual can make adequate amounts to maintain health.
When the hormone controlling concentration of the urine is lost (arginine vasopressin, AVP), the individual is unable to concentrate their urine and passes large amounts of dilute urine.The initial test to look at this would mean a blood and urine test, with nothing to drink overnight if possible, to look at the concentration of salts in the blood and urine (osmolality). This will show if the kidneys are concentrating urine appropriately. In some cases it is not possible to do this having not had a drink overnight due to the degree of urine being passed. Where there is any doubt further tests involving a stimulation test, or measuring urine volume and levels of salt in the blood and urine under controlled supervision and whilst not drinking fluids can be undertaken to confirm the diagnosis.
Treatment of hypopituitarism means replacing the active hormones that aremissing. For the most part, the hormones used to do this are generally exactly the same as those the body would have produced itself. The method by which hormones are replaced can vary dependent upon which hormone is being replaced.
For example with deficiency of thyroid stimulating hormone and thus levothyroxine from the thyroid, replacement is with levothyroxine as a tablet. Growth hormone is a protein and therefore cannot be taken as a tablet as it would be broken down in the stomach. Replacing growth hormone therefore requires this to be injected in to the skin. Oestrogen replacement can be by a tablet, or by a patch or gel that is absorbed through the skin. Testosterone is replaced either using a long acting injection in to the muscle or by using a gel which is absorbed through the skin. Cortisol, is generally replaced using hydrocortisone (cortisol) tablets taken 2-3 times per day as levels fall over 6-8 hours after taking the tablet. Vasopressin can be replaced by a tablet that is absorbed from the stomach or under the tongue, but can also be given as a nasal spray or injection under the skin.
Once on replacement hormones further blood tests are required for most of these to make sure the levels of the hormones are appropriate as well as for safety markers. The latter to avoid problems associated with over-replacement of hormones. Monitoring of these is likely to be lifelong I most cases of hypopituitarism.