Pseudohypoparathyroidism shows the same symptoms as normal hypoparathyroidism without a deficiency of parathyroid hormone. Blood levels of calcium are found to be too low and phosphate too high. Despite a normal or even elevated concentration, parathyroid hormone is unable to exert its effect.
What is pseudohypoparathyroidism?
Pseudohypoparathyroidism, also known as Martin-Albright syndrome, is characterized by the same disease symptoms as hypoparathyroidism. The term hypoparathyroidism can be translated as a deficiency of parathyroid hormone caused by hypofunction of the parathyroid glands. The prefix “pseudo” means “as if” and indicates deficient action of parathyroid hormone when the concentration of this hormone is normal. Parathyroid hormone regulates the concentration of calcium and phosphate in the blood serum. The action of this hormone causes calcium to be released from the bones when needed while promoting the excretion of phosphate by the kidneys. When the level of calcium in the blood decreases or its demand is increased, the production of parathyroid hormone from the parathyroid glands is stimulated. However, as calcium is released from the bones, phosphate release automatically increases because the main material of the bones is calcium phosphate. Increased phosphate concentrations, however, in turn inhibit further calcium release. Therefore, parathyroid hormone also ensures inhibition of phosphate reabsorption via the kidneys. This means that phosphate is increasingly excreted in the urine. Balanced calcium and phosphate levels are critical for electrolyte balance, which is responsible for normal conduction of stimuli in muscle and nerve cells.
Causes
Pseudohypoparathyroidism is thus characterized by a reduced effect of adequately present parathyroid hormone. As a result, hypocalcemia (calcium deficiency) and hyperphosphatemia (phosphate excess) occur in the blood, just as in classic hypoparathyroidism. The result is increased stimulus transmission and excitation states with neurological deficits. In the mode of action of the parathyroid hormone, however, it is not only its correct concentration that is important, but also the smooth functioning of all intermediate steps in the development of its effect. For example, the mode of action of a hormone requires its docking with a corresponding receptor. This receptor mediates the effect of hormones or other bioactive substances and thus brings them to their expression in the first place. However, if a receptor is not in order, the hormone, in this case the parathyroid hormone, cannot fulfill its function. The same deficiencies occur as in the case of a real deficiency of parathormone. The corresponding defects at the parathormone receptors are genetically determined. The processes at these switching points are complicated and diverse, so that there are four different possibilities for malfunctions. In type Ia pseudohypoparathyroidism, the amount of G protein in the parathyroid hormone receptor complex is reduced. Type Ib is directly characterized by a defect in the PHT receptor. A defect in the catalytic unit of the parathyroid hormone receptor leads to type Ic pseudohypoparathyroidism. Finally, in type II, the receptor is intact. However, the intracellular response is absent here.
Symptoms, complaints, and signs
In addition to the deformities of the physique, the symptomatology in pseudohypoparathyroidism, as in hypoparathyroidism, is characterized by hypocalcemia. The physique of the diseased is characterized by short stature and shortening of the metacarpal and metatarsal bones. Hypocalcemia produces the symptoms of tetany. This involves paresthesias, pawing of the hands, pointed feet, and cramps in the area of the feet and hands. Furthermore, there is an increased reflex readiness (hyperreflexia). This results in hyperexcitability of muscle and nerve cells. The Chvostek sign and the Trousseau test are positive. In the Chvostek’s sign, there is contraction of the facial muscles when the facial nerve is tapped. The Trousseau test is characterized by a spasmodic contraction of the forearm muscles with pawing of the hands after application and inflation of a blood pressure cuff on the upper arm. The spasms may also manifest in individual organs. Biliary colic, spasms of the heart or lungs then occur.Other symptoms may include hair loss, cataracts, a congested papilla, or dry skin. In severe cases, calcium deposits can occur in the brain, leading to headaches and increasing dementia.
Diagnosis and course of the disease
The clinical picture of pseudohypoparathyroidism usually leads initially to a tentative diagnosis of hypoparathyroidism. Laboratory tests are used to examine the parathyroid hormone concentration. If this is normal, the diagnosis is usually pseudohypoparathyroidism. However, this must be differentiated from the so-called pseudopseudohypoparathyroidism. In pseudopseudohypoparathyroidism, calcium metabolism is normal but Gsa protein activity is decreased.
Complications
Pseudohypoparathyroidism elicits symptoms similar to those of hypoparathyroidism. The same is true for the complications that occur in both diseases. The main symptoms are hypocalcemia and hyperphosphatemia, which are the main causes of various complications. Hypocalcemia may be asymptomatic. However, it can also lead to such symptoms as tetany, increased reflexes and low heart rate. In severe cases, cardiac arrhythmias and heart failure occur, posing a great risk of cardiac arrest with failure of the cardiovascular system. Tetany involves cramps in the hands and feet, which can lead to pawing of the hands and pointed feet. If hypocalcemia persists for a longer period of time, psychological problems often occur, manifested by such symptoms as depression, moodiness or anxiety. Since phosphate is formed in addition to calcium, precipitation of calcium phosphate occurs in the vessels, and regulatory mechanisms eventually result in decreased calcium and increased phosphate in the blood. The calcium phosphates precipitated in this reaction lead to calcification of the brain in particular. The calcium deposits in the brain cause severe headaches and, in extreme cases, can develop dementia. The calcium and phosphate levels can be adjusted well in the course of therapy. However, pseudohypoparathyroidism is not curable because it is genetic. The shape abnormalities of the joints and short stature cannot be influenced therapeutically.
When should you see a doctor?
Pseudohypoparathyroidism should always be treated by a physician. The disease can lead to various complications, and it also does not result in self-healing of the affected person. Therefore, treatment by a physician is essential. As a rule, the doctor should be consulted if the affected person suffers from short stature. In this case, various limbs are severely shortened, which can lead to severe limitations and discomfort in everyday life. Short stature is usually noticed in the course of child development. Likewise, pseudohypoparathyroidism must be treated when the affected person suffers from various muscle complaints. There may be pains in the muscles that occur without any particular reason. Also, the visit to a doctor is necessary if the disease leads to heart problems, dementia or dry skin. If the heart problems are not treated in time, the patient may also have a limited life expectancy. In most cases, pseudohypoparathyroidism can be diagnosed by a pediatrician or by a general practitioner. However, the assistance of specialists is necessary for further treatment.
Treatment and therapy
Because pseudohypoparathyroidism is genetic, this condition cannot be treated causally. Only symptomatic therapies to adjust calcium metabolism are possible. However, the physical impairments such as short stature and shape abnormalities are not treatable. A normal calcium level can only be adjusted with medication. This is done by oral administration of calcium preparations in combination with vitamin D. In the event of a tetany attack, calcium must sometimes be injected intravenously. This requires constant monitoring of calcium and phosphate levels. Prolonged calcium administration can lead to the formation of kidney stones. To avoid an increased calcium concentration in the urine, the administration of a thiazide diuretic may be necessary. In this case, calcium excretion must also be checked regularly.
Prevention
Pseudohypoparathyroidism is a genetic disorder. For this reason, there can be no recommendation for its prevention. However, in cases of familial clustering, human genetic counseling and testing can be used to assess the risk to offspring. It should be noted, however, that the genetic basis is not known for all forms of pseudohypoparathyroidism.
Follow-up
Pseudohypoparathyroidism is a genetic disorder, which means that follow-up care for symptoms is only symptomatic and a cure is impossible. Drug treatment helps to adjust the calcium metabolism. For this purpose, calcium preparations are taken in combination with vitamin D. In cases of tetany attacks, calcium must be given intravenously at times. Calcium intake can lead to the formation of kidney stones. In order to avoid this, it may be necessary to take additional diuretic medication. Calcium excretion should always be monitored. Control examinations at regular intervals by a specialist are recommended. These serve to control calcium and phosphate levels and to adjust medication if necessary. After diagnosis, a healthy lifestyle should be led. A healthy diet with calcium-rich foods helps to reduce the deficiency naturally. Also, the intake of vitamin D through foods such as porcini mushrooms, oatmeal or sweet potatoes has a positive effect on the body. A low-phosphate diet should also be aimed for by reducing protein-containing products, legumes and nuts. Physical impairments such as short stature or shortened metacarpals or metatarsals are not treatable and can lead to severe limitations in everyday life. The overexcitability of the muscles can be trained by physiotherapy. Relaxation techniques such as yoga or meditation also help to better manage the condition.
Here’s what you can do yourself
The options for self-help are very limited in pseudohypoparathyroidism. The symptoms of the disease are extensive and cannot be adequately minimized with one’s own actions. The affected person can positively support his organism by optimizing food intake. Foods containing calcium should be increasingly consumed. The aim is to reduce the existing calcium deficiency in a natural way. Various calcium-containing products should therefore be consumed throughout the day. At the same time, phosphate-containing nutrients should be avoided. Products containing protein, legumes and nuts should therefore be avoided in menu preparation. The excess of phosphate already produced by the body would otherwise be further increased. To further improve health, an intake of vitamin D is recommended. Mushrooms or chanterelles contain the vitamin and should be a regular part of the diet. Dealing with the overexcitability of the muscles can be promoted by specific training or relaxation techniques. In a physiotherapy session, the affected person learns various exercises that should be pursued on his or her own responsibility outside of therapy appointments. In addition, methods such as yoga, meditation or autogenic training help to strengthen mental power. In everyday life, this can be helpful in coping with the disease. Well-being is stabilized and stressors are reduced.
