What is hypomagnesemia with secondary hypocalcemia (HSH)?

Updated: Oct 30, 2020
  • Author: Tibor Fulop, MD, PhD, FACP, FASN; Chief Editor: Vecihi Batuman, MD, FASN  more...
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HSH, also called primary intestinal hypomagnesemia, is an autosomal-recessive disorder that is characterized by very low serum magnesium levels and low calcium levels. [94]  Mutations in the gene coding for TRPM6, a member of the transient receptor potential (TRP) family of cation channels, have been identified as the underlying genetic defect. [22, 23, 24] Patients usually present within the first 3 months of life with the neurologic signs of hypomagnesemic hypocalcemia, including seizures, tetany, and muscle spasms.

Untreated, HSH may result in permanent neurologic damage or may be fatal. Hypocalcemia is secondary to parathyroid failure and peripheral parathyroid hormone resistance as a result of sustained magnesium deficiency.

Usually, the hypocalcemia is resistant to calcium or vitamin D therapy. Normocalcemia and relief of clinical symptoms can be attained by administration of high oral doses of magnesium, up to 20 times the normal intake. As large oral amounts of magnesium may induce severe diarrhea and noncompliance in some patients, parenteral magnesium administration must sometimes be considered. Alternatively, continuous nocturnal nasogastric magnesium infusions have been proven to efficiently reduce gastrointestinal adverse effects.

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