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Hypoparathyroidism is a very rare disorder in which lower than normal levels of calcium in the blood are due to insufficient levels of parathyroid hormone. It is a condition which may be inherited, associated with other disorders, or it may result from neck surgery.
The parathyroids are four tiny glands, situated behind the thyroid gland, whose function is to constantly regulate the calcium level in the blood as variations occur. Even small variations from the norm can impair nerve and muscle function. So, if the level of calcium in the blood drops, the parathyroid glands quickly respond by increasing their output of parathyroid hormone (or parathormone - PTH) which in turn causes the bones to release more calcium into the blood, the intestines to absorb more from food and the kidneys to conserve calcium. If the blood calcium level increases, the glands will reduce their output of PTH and the process is reversed.In rare cases, however, the parathyroid glands may become overactive (Hyperparathyroidism) or underactive (Hypoparathyroidism).
Causes
Hypoparathyroidism may occur for several reasons which fall into two main areas:
A) An inherited condition
Some people may inherit a condition in which they are born without sufficient parathyroid tissue. This is known as Idiopathic Hypoparathyroidism and may be familial or sporadic. Familial idiopathic hypoparathyroidism may be inherited as a sex linked recessive, autosomal recessive or autosomal dominant with variable penetrance.The sporadic form of the condition often affects children and is often associated with Addison's Disease, pernicious anaemia or premature ovarian failure. Autoantibodies to cytoplasmic parathyroid tissue are found in 30-70% of patients with idiopathic hypoparathyroidism.
Some people are resistant to the PTH hormone action itself as in Pseudohypoparathyroidism. This is a hereditary disorder characterized by an inadequate response to the parathyroid hormone, although this hormone is present in normal amounts. This inadequate response affects bone growth in patients with this disorder, headaches, weakness, easy fatigue, lack of energy, and blurred vision light may also occur.Patients who express only the AHO phenotype are described as having Pseudopseudohypoparthyroidism. They have normal serum calcium levels and have no other evidence of hormone resistance.
B) As a result of surgery
Deficient parathyroid secretion can occur when the parathyroid glands have to be removed because of overactivity or a tumour. More rarely, this may also occur during thyroid or laryngeal surgery when the parathyroids may be inadvertently removed or damaged. In these cases, deficiencies are less likely to be due to the chemotherapy or radioiodine treatment recieved after cancer operations, as is often believed, and more likely to be due to an inexperienced surgeon. Check out your surgeon carefully! How many of these operations have they done? The risk of hypoparathyroidism is reduced in the hands of an expert surgeon, but there is always a small risk nevertheless, depending on the location of the parathyroids and the complexity of the operation. Many thyroid cancer patients find themselves coping with calcium problems after their operation (See 'Related conditions'. Reoperative neck surgery (i.e. a second or further operation in a previously operated neck) carries a somewhat increased risk of parathyroid damage. In some people the parathyroids may recover in time but other people develop Hypoparathyroidism as a result, although this may not be immediately evident.
HPTH can also be caused by surgery for Hyperparathyroidism (i.e. to remove overactive parathyroid(s)) See 'Related Conditions'.
Symptoms
Whatever the cause, Hypoparathyroidism presents with symptoms of low calcium or Hypocalcaemia. For some people symptoms will be acute, requiring rapid treatment while for others chronic hypocalcaemia may be well tolerated although treatment is necessary to prevent long term complications and may require adjustments over time. So while very mild hypocalcaemia can be asymptomatic, it can also present as a severe life threatening condition and falling levels will produce tetany of varying degrees. Symptoms can range (sometimes in a matter of minutes) from 'pins and needles' of the face, hands and feet, weakness, muscle spasms in the hands and feet, muscle twitches or cramps all over, sensations such as tingling, vibrating, burning and numbness (paresthesias), 'foggy' brain, dizziness, irritability, sensitivity to noise and acute anxiety to, if untreated, severe muscle paralysis throughout the body, seizures or fits if levels drop too far and too fast. Hypercalcaemia or high calcium levels, on the other hand, produce headaches, nausea, vomiting, heavy and painful limbs, dizziness and, if untreated, kidney failure.
It is important to note here that responses are highly individual: different people may experience a different set of symptoms or the same person may experience different symptoms on different days although tests give the same reading. People may also experience symptoms when blood tests are normal. There are many influences on calcium levels apart from medication such as diet, alcohol, caffeine, exercise, stress, infection or illness and exercise.
Twitching of the facial muscles or lip on tapping the cheek (Chvostek Sign)is a helpful early indication of low calcium. A carpopedal spasm, a cramp of wrist and thumb which can be induced after inflating a blood pressure cuff (Trousseaus Sign) is another, more painful, one.
Long term symptoms may affect teeth, nails, hair and skin, and there may be calcium deposits or kidney stones. Anxiety and depression may be present as low calcium is linked to the emotions and there may also be problems with memory and general fogginess. Fatigue and muscle weakness is common.
Treatment
Hypoparathyroidism requires lifelong treatment of oral supplements of calcium, Vitamin D, in varying forms,and magnesium. These levels are checked regularly by blood tests. Acute symptomatic hypocalcaemia, however, requires urgent correction with intravenous calcium. As yet there is no synthetic form of PTH available for treatment. As this is a rare condition and it's effects are so individual and unpredictable, it is important that we learn to recognise our own unique set of symptoms and monitor the ways in which they relate to medication and other influences in order to maintain stable levels. Hopefully, sharing such information on this website and working together with our doctors will move us towards this goal and so improve our quality of life.
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