This system is an extensive one found almost all over the body. It is concerned with hormone production. A hormone is a substance produced in one part of the body (typically a gland) and exerts its effect on other parts of the body, nearby and distant. There are quite a number of different sites of hormone production including:
- the hypothalamus in the brain
- the pituitary gland located close to the hypothalamus
- the thyroid gland in the front of the neck which produces thyroid hormones
- some specialised cells in the pancreas called islet cells which produce insulin and some other hormones
- the adrenal glands on top of the kidneys which produce adrenaline
- the testes and ovaries which produce sex hormones
The functions of some important hormones are as follows:
- The hormones of the hypothalamus are majorly ‘releasing hormones’ which act on the pituitary gland to ‘release’ its own hormones.
- The hormones of the pituitary gland are called ‘trophic hormones’ because they stimulate the ‘target organs’ to produce ‘target hormones’.
- The thyroid hormone helps in the body’s metabolism.
- Insulin helps the body use glucose by driving it into the cells where they are used to generate energy.
- Adrenaline is a ‘fright, flight and fight’ hormone which enables the body cope with fear and stressful situations.
- The sex hormones testosterone, oestrogen and progesterone help in reproduction.
The production of these hormones is regulated, and their underproduction or overproduction leads to various disease conditions. There are two principal ways through which this regulation occurs:
Negative feedback mechanism:
This is the commonest method of regulation. Here, the hypothalamus produces a ‘releasing hormone’.
This acts on the pituitary gland to produce a ‘trophic hormone’.
This then stimulates the ‘target organ’ such as the thyroid gland to produce a ‘target hormone’, in this case the thyroid hormone. The thyroid hormone then goes on to perform its functions on various organs of the body.
When each of these hormones reaches a particular level in the body, it will act on the organ stimulating its production to stop producing.
Positive feedback mechanism:
A common example of this is what happens during childbirth. Stretching of the cervix by the baby causes the hypothalamus to produce a hormone called oxytocin. This causes the uterus to contract even more, pushing the baby against the cervix and stretches it the more until the baby is delivered.
Symptoms of Endocrine Diseases
There are a number of symptom complexes that particularly suggest endocrine disease. They include:
- Excessive thirst and increased urine production
- Weight loss
- Weight gain or redistribution of body fat
- Muscle weakness
- Cold intolerance
- Heat intolerance
- Increased sweating
- Awareness of heartbeat
- Postural unsteadiness
- Visual disturbance
- Cramps and ‘pins and needles’ sensation
- Swallowing difficulty
- Neck pain and swelling
- Breast tissue in males
- Absence of menses
- Inappropriate production of breastmilk
- Excessive hair growth
- Constipation or diarrhoea
- Skin changes
It is necessary to consult your doctor when you notice any of these symptoms especially when they are bothering you. They may be able to find out if anything is wrong after proper evaluation.
Excessive thirst and increased urine production
Excessive thirst (polydipsia) and increased urine output (polyuria) are the most important presenting symptoms of diabetes mellitus. They may also be due to kidney problem with the kidney’s concentrating ability. Sometimes, apparent polydipsia and polyuria may be due to increased fluid intake, which at its most extreme may be vastly excessive.
Loss of weight is a feature of decreased food intake or increased metabolic rate. Sometimes both factors may operate to reduce body weight, as in the weight loss of cancer. Thyroid over-activity (hyperthyroidism) is nearly always associated with a combination of weight loss and increased appetite. Weight loss can also be found in diabetes mellitus.
Anorexia nervosa, a psychological disorder characterized by a long period of low body weight in the absence of other features of ill health, is common in young women. Any form of weight loss may be associated with lack of menses.
Weight gain or redistribution of fat
An increase in body weight is a predictable result of a reduction in metabolic rate. Weight gain is therefore a common feature of thyroid under-activity (hypothyroidism). However, obesity is rarely a consequence of specific endocrine dysfunction, an exception being very rare phenomenon of leptin deficiency. In the majority of patients, ‘simple obesity’ is due to a longstanding imbalance between energy intake and expenditure; it frequently begins in childhood and is often present in more than one family member. The excess of a hormone called glucocorticoid results in an increase in body fat especially in the abdomen and at the back (truncal obesity) with paradoxical thinning of the limbs.
Muscle weakness not due to neurological disease is a feature of several metabolic disorders, including over-active thyroid (thyrotoxicosis) and vitamin D deficiency. The major symptom
is difficulty in climbing stairs, boarding a bus or rising from a sitting position. The muscle weakness of vitamin D deficiency is often painful, in contrast to other causes.
Cold or heat intolerance
An abnormal sensation of cold, out of proportion to that experienced by other individuals, may indicate underlying hypothyroidism.
The increased metabolic rate of thyrotoxicosis may be associated with heat intolerance in which, at its most extreme, the patient is comfortable at a temperature that others find unpleasantly cold.
Hyperhidrosis (excessive sweating) may be characterized by onset in childhood or adolescence and, sometimes, by a family history. A recent increase in sweat secretion, on the other hand, may be an early indication of thyroid over-activity. Sweating is a common feature of anxiety. Intermittent sweating after meals may occur in some conditions affecting the nervous system. Growth hormone excess (acromegaly) also increases sweating.
Trembling at rest which is hardly noticeable by mere looking is one of the main features of thyrotoxicosis. It is different from the more easily noticeable and more irregular tremor of anxiety. Tremor due to neurological disease is even more obvious and slower in rate, as in Parkinson’s disease.
Awareness of the heartbeat
Palpitations are a heightened, unpleasant awareness of the heartbeat. They may be a feature of thyrotoxicosis, but are more likely to be due to anxiety.
Awareness of the heartbeat while lying down is normal. The sensation of intermittent forceful cardiac contraction, is usually a normal phenomenon.
Dizziness, or a sensation of faintness on standing may be due to a fall of diastolic blood pressure on standing (postural hypotension). It occurs with reduced blood volume. Postural hypotension is frequently due to a neurological disease, especially in longstanding diabetes mellitus. It is also a common complication of any drug therapy for hypertension.
Several endocrine conditions may cause visual problems.
Decreased vision may be due to compression of the optic nerve by tumours around the eye or eye swelling due to thyroid disease. Double vision (diplopia) may occur in thyroid eye disease. Apparent magnification of vision can occur in low blood sugar.
Cramps and ‘pins and needles’ sensation
Intermittent cramp and ‘pins and needles’ (paraesthesiae), especially if on both sides of the body, can be due to low calcium in circulation. However, the causes of paraesthesiae in the hands includes nerve compression at the wrist.
This is a rare symptom of endocrine disease. It is an important presenting feature of reduced adrenal hormones, in which typically it is maximal in the morning and may be associated with vomiting. Similar symptoms may occur with excess calcium in the blood. Occasionally, thyrotoxicosis may present with nausea and vomiting.
Difficulty in swallowing is an unusual manifestation of endocrine disease but may occur in thyroid enlargement.
Neck pain and swelling
Discomfort in the neck may lead to the incidental finding of thyroid enlargement. Modest degrees of thyroid enlargement are very common, whereas pain arising from the thyroid is relatively unusual. Rapid enlargement of the gland, especially in an elderly person, suggests a thyroid cancer.
Reduced erectile potency may be a consequence of primary abnormalities, such as the following:
- Decreased blood supply to the penis.
- Neurological disease (e.g. following diabetes)
- Testosterone deficiency.
- Drug therapy (e.g. certain antihypertensive drugs).
- Psychological factors (situational impotence).
Breast tissue in males
Gynaecomastia refers to a smooth, firm, mobile, often tender disc of breast tissue under the areola in the male. It is different from the soft, fatty enlargement often seen in obesity. Mild gynaecomastia (sometimes on one side) frequently occurs as a temporary phenomenon in normal puberty and may persist for several years, or sometimes indefinitely. In adults, it may result from:
- excess ‘female hormone’ (oestrogen)
- reduction in circulating ‘male hormone’ (testosterone)
- blockage of the action of the ‘male hormone’.
Absence of menses
The term amenorrhoea describes absence of menstrual periods (menses). Perhaps the most common cause of failure of onset of menses (primary amenorrhoea) is ‘normal’ delay of puberty.
Important abnormal causes include hormonal deficiency from any cause and defects in lower genital tract development (some females are born with an abnormal or absent womb and/or vagina).
Secondary amenorrhoea (cessation of previously established menses) has similar causes. In addition, marked weight loss may lead to amenorrhoea, as in anorexia nervosa. Amenorrhoea, or oligomenorrhoea (infrequent scanty periods), may occur in women who perform excessively rigorous physical training programmes. Normal pregnancy is the most common cause of secondary amenorrhoea.
Inappropriate production of breastmilk
Occasionally, normal production of breastmilk may persist after breastfeeding has ceased. Inappropriate production (galactorrhoea) is usually on both breasts. Milk production is under the influence of a hormone called prolactin produced by the pituitary gland. Any condition that causes inappropriate production of the hormone will lead to galactorrhoea. Examples are tumours of the pituitary gland, hypothyroidism, and some drugs. However, even with very high prolactin levels, galactorrhoea is rare in men.
Excessive hair growth
An increase in the growth of facial and body hair in adult females is called hirsutism. It is a relatively common symptom and may be due to increased circulating ‘male hormones’ (androgens). However, it is most commonly a normal characteristic.
Abnormal causes of hirsutism include diseases of the ovary and the adrenal gland which may cause them to produce androgens. Increased libido suggests substantially increased androgen secretion, which may be either ovarian or neoplastic in origin.
Constipation or diarrhoea
Constipation and abdominal swelling may be features of thyroid or pituitary gland problem. Diarrhoea may occur as part of nerve damage involving the gut in diabetes mellitus.
The skin may become pale in conditions affecting the testes or pituitary gland. Darkening of the skin and increased sebum production causing greasy skin and acne on the face and shoulders occurs in high levels of adrenal gland hormones. In deficiency of adrenal gland hormones, there is darkening of the conjunctival membrane beneath the eyelids and of the inside of the mouth, the axillae and the palmar skin creases.
Low levels of thyroid hormones may cause the skin to appear dry, pale, sallow or even slightly yellow. Excess thyroid hormone production may cause the skin to be dry and hot.
Low calcium levels may cause the nails to be friable. Purplish skin discolouration may be due to hormones secreted by tumours in the gut or lung.
Patchy white areas of the skin (vitiligo), is common in association with thyroid under-activity and vitamin B12 deficiency.