Hypoparathyroidism Tied to Rare Heart Muscle Disease in Woman

Hypertrophic cardiomyopathy an unusual complication of hypoparathyroidism

Teresa Carvalho, MS avatar

by Teresa Carvalho, MS |

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An illustration of a woman's heart.

Hypoparathyroidism was associated with hypertrophic cardiomyopathy — heart disease marked by thickened heart muscle, so that the heart pumps blood less effectively — in a 73-year-old woman, according to a case study.

This rare finding was reported in “Hypertrophic cardiomyopathy in a patient with secondary hypoparathyroidism: A case report,” published in the journal Radiology Case Reports.

Hypoparathyroidism is characterized by low levels of parathyroid hormone (PTH), which controls the levels of calcium and phosphorus in the blood.

When this hormone is lacking, blood calcium levels drop (hypocalcemia), while blood levels of phospate (a molecule that contains phosphorus) rise, a condition known as hyperphosphatemia.

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Woman developed hypoparathyroidism secondary to surgery decades ago

Hypocalcemia may be related with temporary dilated cardiomyopathy, a disease of heart muscle that causes the heart’s chambers (ventricles) to thin and stretch, becoming larger and weaker. Dilated cardiomyopathy also affects the heart’s ability to pump blood efficiently.

People with chronic hypoparathyroidism with hypocalcemia can experience cardiac symptoms that include an abnormal heart rhythm and heart failure. High levels of phosphate in hypoparathyroidism patients also may increase the levels of a molecule called fibroblast growth factor-23 (FGF-23), a bone-derived hormone that lowers blood phosphate levels. This causes calcium to accumulate in heart tissues (calcification), leading to cardiomyopathy.

Researchers in Colombia detailed the case of a 73-year-old woman with chronic hypoparathyroidism and hypocalcemia who developed hypertrophic cardiomyopathy, instead of more expected dilated cardiomyopathy. She was under treatment for chronic heart failure.

The patient was admitted to the hospital several times due to frequent accumulations of fluid between the layers of the pleura (the lining of the lungs), shortness of breath, and hypocalcemia.

She developed hypoparathyroidism secondary to a surgery she had, nearly 55 years ago, that removed most of her thyroid gland. Her medical history also included high blood pressure, cataracts (clouding of the eye lens), epilepsy, and cognitive impairment.

At physical exam, she showed Chvostek sign, a twitching of the facial muscles, and Trousseau sign, a spasm of the muscles of the hand and wrist. Both are related with hypocalcemia.

Blood tests found low levels of calcium and PTH, and high levels of phosphate. Imaging tests revealed several cardiac issues, such as an enlarged heart, calcification, dilatation of the right ventricle and of both atria (the heart’s upper chambers), and high blood pressure in the arteries of the lungs.

Results were compatible with apical hypertrophic cardiomyopathy, a condition in which the left ventricle is abnormally enlarged.

“The hypoparathyroidism-associated hypertrophic cardiomyopathy is an exotic manifestation of chronic hypoparathyroidism; it is even rarer than hypocalcemic dilated cardiomyopathy,” the scientists wrote.

“It seems to be the consequence of hypoparathyroidism, a high calcium phosphate product, and hyperphosphatemia, leading to increased FGF-23 and posterior activation of intracellular pathways, causing cardiac hypertrophy,” they added. Of note, calcium-phosphate product is obtained by multiplying blood serum calcium and phosphate levels.

According to the team, FGF-23 may have proinflammatory effects that could contribute to heart inflammation and enlargement.

“The low occurrence of cardiomyopathy [in patients with hypoparathyroidism] suggests that there must be a subtype of vulnerable patients, with risk factors not yet defined,” the researchers wrote.

The woman started treatment with calcium supplements and calcitriol, the active form of vitamin D, as well as with Forteo (teriparatide), a lab-made parathyroid hormone PTH fragment approved for osteoporosis, marked by weak and brittle bones.

This treatment regimen enabled her to reach near-normal calcium levels, phosphate levels in the upper limit of normal, and calcium phosphate product under a threshold extrapolated from patients with chronic kidney disease.

Her condition improved and, consequently, her hospital visits became less frequent, the scientists noted.