The pituitary is a bean-sized endocrine gland located in the brain. It forms part of the hypothalamus (a gland located further to the centre of the brain and which, together with the pituitary, has the most wide-ranging influence over the entire endocrine system), with which it is connected through a small tube, called the pituitary stalk, and which produces a number of hormones possessing different actions. It is composed of two lobes: the posterior pituitary (also called the neurohypophysis) and the anterior pituitary (also called the adenohyphysis).
The secretion of hormones from the pituitary is controlled by substances secreted by the hypothalamus. The pituitary secretes a variety of hormones, as, for example, adrenocorticotropic hormone (ACTH), luteinizing hormone (LH), follicle-stimulating hormone (FSH), thyroid-stimulating hormone (TSH), growth hormone (GH) and prolactin. These hormones are released into the bloodstream to the respective target organs.
Via the actions of the abovementioned hormones that it produces, the pituitary gland connects the hypothalamus with the other endocrine glands, such as the thyroid, the adrenals, the ovaries and the testes. The hypothalamus has been shown to produce hormones that also exert actions in the adipose tissue of the body, in the gastroenterological system (regulation of appetite) and in the muscles (energy consumption), while it additionally receives messages via the hormones of these organs. It has been called the “master gland” of the body.
When the pituitary produces levels of hormones that are either too high or too low, this will impact directly upon body functioning or else it will affect the endocrine glands with which it communicates.
Diagnosis of hormone levels dysfunction, or hormonal imbalance, is not carried out simply via a blood test since normal fasting rates can sometimes be misleading. Thus, what is required in most cases is diagnosis through suitable intravenous challenge tests to accurately determine hormonal secretion. This is why the specialized endocrinologist, in accordance with each case, will need to decide which is the most appropriate test. Finally, the diagnosis will have to be confirmed and be followed by the right X-ray method.
3) Symptoms – Diseases
Pituitary disorders are very rare, the most common problem being when an adenoma (a non-cancerous, or benign tumour) develops: many of these will never even present symptoms. When symptoms do arise, they can be headaches or visual problems, or the tumour will press on the pituitary gland, this either preventing it from producing one or more hormones or causing it to produce too much.
Some symptoms caused by compression by a pituitary tumour of surrounding tissues are: headache, peripheral vision loss, nausea and vomiting, unintended weight gain or loss, sexual dysfunction, etc.
Some diseases arising from dysfunction of the pituitary gland are: galactorrhoea, acromegaly, hypothyroidism, central obesity, hirsutism as well as amenorrhoea and fertility disorders in men and women. As mentioned, pituitary tumours are usually benign at a percentage of 90-95%. Benign pituitary tumours may be inactive; in the cases that they overproduce hormones they are called adenomas. Adenomas are classified according to the hormone that they overproduce or underproduce or to their size.
Treatment of adenomas can be medical or surgical, this depending on the symptoms produced by the tumour. Sometimes the tumour is such that it will merely be followed up without any management, while there are also those that will need some form of medical treatment. However, when the tumour is exerting excess pressure and endangering vital functions, then it must be removed surgically.