Hypocalcemia in dogs
Hypocalcemia in dogs occurs when their blood calcium levels are too low. More than a simple dietary deficiency, hypocalcemia can be a sign of a serious disease and have deleterious consequences on the health of our four-legged companions.
Since it does not always cause symptoms, hypocalcemia in dogs is often discovered incidentally during a check-up at the veterinarian's office. Additional tests are often necessary to determine if the problem is pathological or due to dietary imbalances.
What is hypocalcemia in dogs?
Hypocalcemia in dogs is a calcium deficiency, meaning that the animal's body contains less calcium than it needs to function properly. Calcium is a mineral that is primarily involved in the formation of bones and teeth, but is also critically important in cellular physiology. It is a vital element, without which the dog cannot survive.
In fact, calcium is by far the most important mineral in the dog's body. It is almost completely stored in the dog's bones (about 99%), but also circulates in the blood. Nearly 40% of the calcium circulating in the dog's blood is bound to proteins, particularly albumin.
Although the general public is well aware of the role of calcium in the formation and health of bones and teeth, the essential action of this mineral on other cells of the body, and particularly in cellular exchanges, is more confidential. In fact, calcium is also an electrolyte, that is to say, in short, a conductor of information. Some calcium elements are ionized, charged with ions that dissolve in the blood and produce electrical impulses that allow messages to be sent.
Also, it is an element that participates in neuromuscular functions by impacting the maintenance of blood pressure and the mechanism of muscle contraction, including that of the myocardium (heart muscle). Finally, calcium is involved in certain enzymatic processes and modulates the body's pH, particularly by neutralizing overly acidic environments.
Calcemia, i.e. the level of calcium in the blood, is extremely regulated by the body to avoid variations, which can be rapidly fatal. Calcemia is regulated by two major hormones: parathormone and calcitonin. Calcium balance, which corresponds to normal blood calcium levels, is determined both by calcium intake and absorption, and by calcium loss.
In case of hypocalcemia, the body will try to correct the calcium deficit by drawing on its resources, namely bones and teeth, at the expense of skeletal health. This type of mechanism, for example, leads to losses, which must be compensated for by additional intakes, or by better absorption of current intakes.
Causes of hypocalcemia in dogs
The causes of hypocalcemia in dogs are extremely varied and are essentially associated with three phenomena: a deficit in intake, disorders of absorption and metabolism, or excessive losses.
It should be noted that hypocalcemia is frequently a multifactorial disorder, i.e., caused by several correlated problems.
Hypocalcemia in dogs and poor intestinal absorption
Hypocalcemia in dogs is frequently associated with poor intestinal absorption of calcium and/or vitamin D. Vitamin D is essential for the absorption of calcium in the intestine, its reabsorption in the kidneys and its binding to the bones. A vitamin D deficiency therefore inevitably leads to a calcium deficiency, although this is usually compensated for by the body, to the detriment of bone health.
Unlike humans, dogs cannot synthesize vitamin D from sunlight and must obtain it from their diet. Almost all industrial dog foods are adequately dosed with vitamin D, even the cheapest ones. Vitamin D deficiency is therefore rarely caused by an unbalanced diet - except in cases of true malnutrition, but is more often caused by intestinal disorders that compromise intestinal permeability and prevent nutrients from passing into the body. IBD (chronic inflammatory bowel disease), food intolerances and allergies, viral or bacterial gastroenteritis, parasitosis (intestinal worms) or neoplasia (tumors) of the digestive tract are all possible causes.
Hypocalcemia in dogs with renal or hepatic insufficiency
The kidneys and liver play a significant role in calcium metabolism and absorption in dogs, and renal or hepatic insufficiency can lead to hypocalcemia. Hypocalcemia is frequently associated - in more than half of the cases - with hypoalbuminemia, a deficiency of albumin, a protein essential to the functioning of the dog's body to which calcium is bound.
Albumin is synthesized by the liver, and any dysfunction of the liver (hepatic insufficiency) can cause a drop in the dog's albumin level, which is fatally followed by a drop in blood calcium levels. Renal failure tends to be complicated by hypoparathyroidism, a decrease in the production of parathormone, a hormone that regulates calcium levels in the blood.
Hypocalcemia in dogs and kidney stones
Other disorders of the renal system, called tubulopathies, can disturb the excretion of calcium by the kidneys, resulting in increased losses. In this case, the calcium is not reabsorbed by the kidneys as it should be, but is precipitated to form small stones.
In addition to the problem of urinary and kidney stones that can damage kidney function, this phenomenon causes a drop in the level of calcium in the blood, since it is eliminated from the body when it should remain there.
Hypocalcemia in dogs and abnormal calcium losses
Various phenomena can cause the body to leak or overconsume calcium resulting in hypocalcemia. Eclampsia, or puerperal tetany, is a sudden hypocalcemia that occurs in the lactating bitch that uses too much of her body's calcium during fetal ossification and milk production. It is often fatal and usually occurs within one month of whelping, although it can also occur from late gestation onwards.
Some dogs are predisposed to eclampsia, especially small breeds. Giving birth to a large litter is an additional risk factor. Acute pancreatitis, as well as certain medications and toxins, including ethylene glycol (antifreeze), can also cause sudden hypocalcemia. In case of acute pancreatitis, the dog may suffer from acidosis, i.e. a sudden acidification of the body. The dog is forced to use calcium to neutralize its pH - an absolutely vital process. Excess sodium, which occurs when the dog eats too much salt, can also cause very significant calcium leakage.
Symptoms of hypocalcemia in dogs
In most cases, hypocalcemia in dogs is only biochemical. That is, it is visible in the animal's blood work, but does not cause any symptoms. This abnormality can be attributed to the individual chemistry of each dog's body. Indeed, not all dogs are always within the norms, and we don't really know why.
Finally, it is also possible that minor hypocalcemia does not cause any visible damage to the body, but merely weakens it over time. The severity of the symptoms observed is highly dependent on how quickly the hypocalcemia sets in, how severe it is and how long it lasts. In general, only marked hypocalcemia causes symptoms.
In the case of severe hypocalcemia, which causes an acute crisis such as eclampsia, poisoning or pancreatitis, there is increased restlessness, which is quickly complicated by muscle spasms, tetany and convulsions. Cardiovascular system failures may then occur, mainly due to hypotension and decreased myocardial contractions. If not treated urgently, the dog is in mortal danger.
In the case of chronic hypocalcemia, which is found especially in animals with hypoparathyroidism due to renal failure, or hypoalbuminemia due to liver failure, the symptoms are mainly neuromuscular and nervous. The animal may suffer from seizures, tremors, muscle cramps, tetany (temporary paralysis) and behavioral problems.
The dog has a tendency to adopt a stiff gait, and may be abnormally agitated, irritated, aggressive, hypersensitive to environmental stimuli, and even disoriented. Finally, fever, anorexia, abdominal pain, ataxia, muscle weakness, cataracts, slow pulse, facial itching, and digestive disturbances (diarrhea and vomiting) are also frequently observed in the hypocalcemic dog.
Treatment and prognosis of hypocalcemia in dogs
In most cases, hypocalcemia in dogs does not require treatment because it is asymptomatic. However, management is required for acute attacks or chronic hypocalcemia that cause symptoms. When asymptomatic hypocalcemia is detected, the cause of the hypocalcemia (digestive diseases, renal failure, intestinal tumors, hormonal disorders, etc.) should be investigated and managed.
Acute hypocalcemia is a true veterinary emergency. The dog's prognosis is life-threatening, and treatment consists of administering additional calcium to rapidly correct the deficit. The dog usually needs to remain in the hospital under supervision to ensure that neuromuscular symptoms resolve after an initial injection of calcium - without which a new injection is required - as well as to monitor for possible cardiac complications.
Diazepam may also be used to treat tetanic seizures. In bitches with eclampsia, lactation is often suppressed - the puppies will need to be formula fed - and long-term vitamin D and calcium supplementation is implemented.
FAQ
How do I know if my dog has hypocalcemia?
In most cases, hypocalcemia in dogs is asymptomatic and is discovered by chance during a blood test at the vet's office. However, the sudden appearance of behavioral problems (agitation, aggressiveness, hypersensitivity, disorientation, etc.) or neuromuscular symptoms (tremors, convulsions, cramps, tetany, etc.) may indicate acute hypocalcemia. In this case, it is a vital veterinary emergency.
Can hypocalcemia in dogs be treated?
Hypocalcemia in dogs is a multifactorial disorder, almost always secondary to another problem. While an acute attack can usually be treated when treated urgently, chronic hypocalcemia has a more guarded prognosis. Chronic hypocalcemia may be due to kidney or liver failure, tumor, or chronic bowel disease. In this case, the dog's life is not necessarily in danger in the short or medium term, but it will often need life-long treatment and its longevity may be shortened.
My dog has hypocalcemia, is it serious?
If your dog has a slight hypocalcemia that is only biochemical, i.e. visible in his blood tests, but does not cause any symptoms, he is generally not in danger. Some dogs are not quite up to standard, but it is not clear why. Hypocalcemia in dogs becomes dangerous as soon as symptoms are observed, whether they are behavioral (agitation, aggressiveness, hypersensitivity, etc.), neuromuscular (convulsions, tremors, tetany, etc.) or cardiac (slow pulse, abnormal fatigue, etc.).
Can I give my dog calcium to prevent hypocalcemia?
No, it is strongly discouraged to give calcium to your pet to prevent hypocalcemia without the explicit approval of your veterinarian. In fact, hypocalcemia almost never results from a deficit in calcium intake, but from excessive leakage or from problems in the metabolization and/or absorption of calcium. Therefore, there is no need to worry about your dog getting too little calcium in his diet. Giving your dog extra calcium can cause hypercalcemia, the opposite of hypocalcemia, which can cause equally serious problems.
Should calcium be supplemented in a pregnant or lactating bitch?
It may be advisable to supplement calcium and vitamin D to a nursing, but not pregnant, bitch. To avoid life-threatening mistakes, it is highly recommended that you consult a veterinarian to determine if, when and how much supplemental calcium is needed.
Severe hypocalcemia can have a serious impact on your dog's health, but fortunately, it is usually very mild and causes no symptoms. To avoid any cardiac or neuromuscular complications, it is important to pay close attention to your dog's health.
A healthy diet will reduce the risk of intestinal disorders that compromise calcium absorption, and a healthy lifestyle can prevent certain metabolic diseases that can interfere with its metabolism.