and androgens. Adrenal insufficiency may be acute or chronic. Symptoms of chronic adrenal insufficiency include low blood pressure, fatigue, weight loss, anorexia, nausea, vomiting, abdominal pain, salt craving and low blood sugar. Skin, especially the skin creases, and mucous membranes such as around the gums, may show increased pigmentation. The loss of secondary sex characteristics is more likely to occur in women with the disease, as men are less reliant on adrenal androgens given that they can also produce sufficient testosterone from the testes.
Acute adrenal insufficiency is a medical emergency and must be identified and promptly treated. The hallmarks of acute adrenal insufficiency are circulatory collapse with abdominal pain and low blood sugar. In the emergency situation hydrocortisone is given by injection, either into the vein or into the muscle. Thereafter, cortisol is replaced with daily hydrocortisone or prednisolone tablets and aldosterone is replaced with fludrocortisone tablets. It is important to know that during illness it is necessary to increase the intake of hydrocortisone tablets to replicate the increased steroid production that the body would usually make in times of illness (but is unable to do so due to failure of the adrenal glands).
Sometimes secondary adrenal insufficiency might occur if a patient has been on steroid treatment for a long period of time, for example, to treat asthma, or other chronic inflammatory diseases. These steroids, especially if given at high doses for a prolonged duration, can cause negative feedback on the hypothalamus / pituitary to reduce the production of ACTH This reduction in ACTH can, in turn, lead to reduced production of steroids by the adrenal glands, which can in time wither due to lack of stimulation. If the steroid medication is stopped abruptly, this can leave patient deficient of any steroids as the adrenal glands can no longer make enough steroids. This can be a dangerous situation as steroids are necessary for health. Therefore, gradually 'weaning' down doses of steroid medications, especially if they have been used for a prolonged period is advisable, under medical supervision, to ensure that the adrenal glands are able to work properly again, and produce the required amount of steroids for health before the steroid medication is stopped.
Overproduction of androgens is rare but may result in excessive hair growth and menstrual period disturbances. Tumours of the adrenal gland are mostly benign, but sometimes result in over- or under-production of adrenal hormones. Adrenal cancer is very rare. Adrenal tumours may require surgery if they are large or overproduce hormones.
Phaeochromocytoma is a tumour of the adrenal medulla, and can release excess amounts of catecholamines. This can lead to high blood pressure, headaches, sweating, tremors and fast heart rate. Most of these tumours are discovered incidentally when people undergo scans for other reasons, although some may be linked with conditions that run in families such as Von Hippel Lindau disease.
The treatment of each disorder varies according to the specific cause. Patients with any concerns about these conditions should seek advice from their doctor or an experienced healthcare professional.
The hypothalamus
Where is my hypothalamus
The hypothalamus is located on the undersurface of the brain. It lies just below the thalamus and above the pituitary gland, to which it is attached by a stalk. It is an extremely complex part of the brain containing many regions with highly specialised functions. In humans, the hypothalamus is approximately the size of a pea and accounts for less than 1% of the weight of the brain.
What does my hypothalamus do?
One of the major functions of the hypothalamus is to maintain homeostasis, i.e. to keep the human body in a stable, constant condition.
The hypothalamus responds to a variety of signals from the internal and external environment including body temperature, hunger, feelings of being full up after eating, blood pressure and levels of hormones in the circulation. It also responds to stress and controls our daily bodily rhythms such as the night-time secretion of melatonin from the pineal gland, diurnal changes in cortisol (the stress hormone) and body temperature over a 24-hour period. The hypothalamus collects and combines all this information and puts changes in place to correct any imbalances.
What hormones does my hypothalamus produce?
There are two sets of nerve cells in the hypothalamus that produce hormones. One set of cells sends the hormones they produce down through the pituitary stalk to the posterior lobe of the pituitary gland where these hormones are released directly into the bloodstream. These hormones are anti-diuretic hormone (also known as Vasopressin) and oxytocin. Anti-diuretic hormone regulates the amount of fluid in the body and causes water reabsorption at the kidneys thus preventing dehydration. Oxytocin stimulates contraction of the uterus in childbirth and is important in breastfeeding.
The other set of nerve cells produces stimulating and inhibiting hormones that reach the anterior lobe of the pituitary gland via a network of blood vessels that run down through the pituitary stalk. These regulate the production of hormones that control the gonads, thyroid gland and adrenal cortex, as well as the production of growth hormone, which regulates growth, and prolactin, which is essential for milk production. The hormones produced in the hypothalamus are corticotrophin-releasing hormone, dopamine, growth hormone-releasing hormone, somatostatin, gonadotrophin-releasing hormone and thyrotrophin-releasing hormone.
What could go wrong with my hypothalamus?
Hypothalamic function can be affected by head trauma, brain tumours, infection, inflammatory diseases, surgery, radiation and significant weight loss. It can lead to disorders of energy balance and thermoregulation, disorganised body rhythms, (insomnia) and symptoms of pituitary deficiency due to loss of hypothalamic control. Pituitary deficiency (hypopituitarism) ultimately causes a deficiency of hormones produced by the gonads, adrenal cortex and thyroid gland, as well as loss of growth hormone. Prolactin however may increase due to loss of negative feedback from dopamine.
Lack of anti-diuretic hormone production by the hypothalamus causes diabetes insipidus. In this condition the kidneys are unable to reabsorb water and produce more concentrated urine. As a result too much water is passed through the body as dilute urine. Patients thus have excessive thirst as their bodies try to make up for the increased loss of water.