It is possible for hormonal production of the pituitary gland to become abnormal. The main reason for this is when tumors (growths) commence to grow either in the gland or close by. These may produce two sets of irregularities. One will be an increased or decreased amount of hormones coming from the gland. The other will be mechanical disorders associated with a growing tumor pressing on surrounding structures. The most notable is the effect on vision, for the gland is very close to the optic nerves, and frequently visual disturbances are the first symptom the patient notices.
Tumors may be benign (noncancerous) or malignant (cancerous). The most common tumor found growing in the pituitary is called a Nonsecretory Chromophobe Adenoma. There is no need to try to remember the names, for these are mainly of academic importance. It is a noncancerous growth.
Other growths that may occur are those that can themselves secrete hormones. These include Eosinophil Adenomas (that may manufacture growth hormone), and others that may secrete ACTH. Other tumors may occur in this region, and some may be cancerous, most frequently being “secondary” deposits from a primary source in some other part of the body.
The significance of this is that the patient may notice some abnormal symptom, leading to a request for medical advice. The symptoms may be of a local nature, or may indicate that an abnormal amount of hormone is circulating in the bloodstream. Quite often, discovering the growth may be an accidental finding when X-rays. CTs or MRI examinations of the skull are taken for other purposes. This is much the same, in principle, as discovering a person has high blood pressure or diabetes when routine examinations are being carried out, such as for life-insurance purposes.
A survey in a large London endocrine clinic recently showed that of every hundred patients coming along, forty percent had local symptoms. Fifty-seven percent had endocrine symptoms, and in three percent of cases, the discovery was accidental.
The local symptom most common is a headache. Another frequent complaint involved visual defects. The tumor had pressed on the “optic chiasma” (part of the optic nerve pathway), and this had obliterated a significant section of the patient’s normal visual field. The patient may have been bumping into people on the pavement, simply through failure to see them, which is a very unusual situation, and one calling for immediate investigation. Others noted the development of a squint (becoming cross-eyed) for no obvious reason. Usually the symptoms came on over a period of time. Seldom do they develop rapidly and dramatically, and for this reason may have existed for some time before being noticed.
Endocrine symptoms occur as the most common type of tumor, the chromophobe adenoma, increases in size, as it does so it tends to compress the pituitary gland, and simultaneously the production of the hormones is gradually reduced. However, this happens at an irregular rate. Gonadotrophin is the first to be lost. This is followed by the growth hormone, then TSH, while ACTH is the last one to be affected.
Different tumors can have varying effects, and it may depend on their location as to the order of interference with hormonal production and release. For instance, lesions above the pituitary may interfere with the antidiuretic-hormone (ADH) releasing mechanism, so permitting the onset of the disease known as diabetes insipidus, which is characterized by excessive water loss.
If gonadotrophin secretion fails before puberty, the result will be lack of commencement of menstrual periods in females, and delayed sexual development in males. In older women, a sudden cessation of menstruation may take place. Sometimes, a male may complain of the onset of impotence and loss of sexual libido. Growth hormone deficiency is most apparent in children where stunted growth is noticed.
A deficiency in TSH will give a clinical picture of an underactive thyroid gland. Fortunately, in the total picture the occurrence of pituitary tumor is rare, but it must be considered in cases of apparent hormonal disturbances. Today the diagnosis is still often difficult, but the availability of accurate tests (essentially radioimmunoassay and others) is making it simpler, quicker and much more reliable.
Unrelated hormonal production in other areas, a strange situation, may occur, giving rise to endocrine anomalies unrelated to the actual endocrine gland itself. This may arise when certain tumors develop in the system and commence producing hormones themselves. They are nearly always malignant (cancerous).
They may arise in a wide variety of organs. These include the bronchi of the lungs, the thymus gland in the lower part of the neck; in breast tissue; the thyroid gland; pancreas; kidney; trachea; ovary and uterus, as well as other tissues.
Sometimes more than one hormone is manufactured. Generally, the hormone produced will be the one usually manufactured by that organ, but this is not always the case. Often the hormones produced have an identical physiological function as the hormones naturally and normally produced by the endocrine gland itself.
ACTH hormone may be produced with oat-cell cancer of the bronchus, as well as in other sites. It tends to complicate an already overcomplicated picture, and can test the ingenuity of physicians dealing in this area. This is why many patients with symptoms suggesting endocrine anomalies are best treated in major hospital centers fully equipped with facilities to diagnose accurately and treat whatever abnormality happens to be present. Generally speaking this is the best place, and symptoms suggesting endocrine imbalances should receive prompt, specialized medical attention.