The function of the hormones are to maintain long term stabilization of the body’s processes such as growth, metabolism and sex, the more immediate adjustments being left to the nervous system, although there are intimate connections between the two in the form of the ‘hypothalamo-pituitary axis’. This means that the disorders of the endocrine system are generally insidious in onset but have subtle and far reaching affects. Pituitary hormones act on a single tissue or organ, sometimes called a ‘target organ’ the hormones produced in turn by these target organs have a wide variety of activities which depend on a steady supply of the stimulating hormones, and most forms of disorders are therefore caused by an under or over production by these glands.
This gland which is the conductor of the whole glandular orchestra is safely tucked away at the base of the brain, being accessible to the surgeon only via the upper recesses of the nose. Being only the size of a pea, it is responsible for nine hormones and damage to this gland has very far reaching consequences. Fortunately disorders are rare although occasionally a benign tumour will cause an over secretion of the gland resulting in hypopituitarism.
This condition is sometimes called ‘Simmonds disease’ a loss of the secretions of the anterior pituitary gland occurs often as the result of a head injury or haemorrhage. When this occurs the patient suffers from the loss of hormones stimulating growth, sexual development, pigmentation and the thyroid and adrenal glands also suffer. In addition the lactating hormone fails causing the milk production to dry up in lactating mothers. If this condition occurs before puberty the subject never grows up and remains small and sexually under developed.
This is another possible consequence of injury to the pituitary, but in this case it is the posterior lobe which is affected, resulting in a loss of the anti-diuretic hormone. This hormone enables the kidney to conserve water by concentrating urine, so its absence results in the passage of large quantities of very dilute urine, up to four gallons a day. The main symptoms are thirst, nocturia and constipation and the treatment usually involves taking the anti-diuretic hormone in the form of nasal drops.
This is an example of over production of a pituitary hormone caused by a benign tumour in an adult. The hormone concerned is the growth hormone and leads to an enlargement of the hands, feet and jaw as well as the soft tissues. This results in general coarsening of the features, a thick tongue, fatigue, aches and pains and increased sweating. Moreover the expanding tumour may give rise to headaches and pressure on the nearby optic nerve leads to defects in the visual field.
In the very rare event of the condition occurring in children it is known as giantism and the child or adolescent will start to develop exceptional stature if they are still in the growing state.
The Thyroid Gland
This ‘H’ shaped which sits in front of the trachea is the one with the highest failure rate. When this happens the gland will often enlarge to form either a smooth or lumpy nodular swelling called ‘a goitre’ Goitres may result from a lack of iodine in the diet. The thyroid, is for some reason very susceptible to attack
by antibodies, which may lead to an over or under production of thyroxine and cause hyperthyroidism or hypothyroidism. Hyperthyroidism or thyrotoxicosis occurs when the thyroid escapes control of the TSH from the pituitary and begins to produce increasing quantities of thyroxine under the influence of another hormone called ‘long-acting thyroid stimulator’ or LATS which acts as a sort of ‘counterfeit’ TSH, while TSH itself is suppressed. LATS also causes enlargement of the pad of fat behind the eye, leading to the familiar bulging eyes or exophthalmos, which is a noticeable feature of what is sometimes called Graves disease.
It is most frequently seen in young women who notice increasing exhaustion, nervousness, insomnia, sweating and palpitations, symptoms which might easily be put down to anxiety. The increasing amount of energy being used is obtained by an enlarged appetite but with a considerable loss of weight, tremor of the hands is caused by the bounding circulation which also leads to high blood pressure and even atrial fibrillation and dyspnoea. Peristalsis also increased and causes diarrhoea or more frequent normal stools while the periods become scanty or cease altogether. The eyes feel inflamed and gritty and double vision may occur if the muscles are affected.
Such a florid picture is seldom seen and in older people the signs may be restricted to palpitations and wasting of the muscles with no goiter or exophthalmos. In them it is often a small overactive thyroid nodule which is the problem and this is another form of hyperthyroidism.
There are three conventional avenues of treatment – by antithyroid drugs, by removal of part of the gland – thyroidectomy or by destruction of the gland with radioactive iodine. The drug treatment is normally tried first, but may result in relapse when the drug is stopped, surgery is the usual approach and works in the great majority.
Hypothyroidism or myxoedema can be the result of pituitary failure but is more often due to damage to the thyroid itself by inflammation, drugs such as lithium, removal of too much of the gland for thyrotoxicosis or most often from an autoimmune
process causing destruction of the gland known as Hashimoto’s disease. The term ‘myxoedema’ refers to the mucilaginous substance deposited under the skin giving it a puffy yellow coarse appearance, but differing from true oedema in that it does not pit under pressure. It is one of the most common and most subtle of the endocrine disorders arising usually in middle aged women around the time of the menopause and leading to weakness and fatigue rheumatic pains and loss of appetite.
The Adrenal Glands
These glands are each actually double glands, one inside the other, each arising from different embryonic tissue. The central part, the medulla, derives from nervous tissue and secretes the hormones adrenalin and noradrenalin. It seldom malfunctions except in the very rare instance of a benign tumour secreting the substances in excess. This causes symptons of sweating, palpitations headache and hypertension along with a degree of panic from the rush of adrenalin. However it is more commonly the cortex which malfunctions either over or underproducing the hormone cortisone and leading to Cushings syndrome or Addisons disease.
Cushings Syndrome is a collection of symptoms arising from an excess of circulating steroid hormones in the body, and can occur in those being treated with long term cortisone for asthma, rheumatoid arthritis or one of the collagen diseases. It may also be caused by a tumour in the cortex stimulating an overproduction of steroid hormones.
Whatever the cause the symptoms are seen first in the face which becomes rounded and moon-shaped with reddening and acne. The trunk also swells and stretch marks and bruises appear on the skin. The fat over the shoulders increases and the bones become thin and brittle and the spine starts to collapse, leading to the familiar ‘buffalo hump’ it is only a minority of those treated with cortisone who develop this syndrome, for it is related to the dosage of the drug as well as the duration of use.