Learning objectives
- •
Symptoms of mild hypocalcemia.
- •
Diagnosis of hypocalcemia, appropriate laboratory studies.
- •
Management of mild hypocalcemia.
The case study
Reason for seeking medical help
About 3 weeks ago, Mrs. RL, a 52-year-old Caucasian woman, had a comprehensive metabolic profile done as part of her annual medical check which revealed a marginally low serum calcium level: 8.3 mg/dL (normal range 8.5–10.2). She is essentially asymptomatic and is referred to the bone clinic to manage her marginally low serum calcium level.
Past medical/surgical history
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Fractured left radius roller skating at age 12.
- •
Hysterectomy at age 42 years, hormonal replacement therapy for 3 years.
- •
Basal cell carcinoma surgically removed about 3 years ago.
- •
Seasonal allergies.
- •
She is unable to tolerate dairy products and has avoided them since she realized her possible intolerance, when she was in her mid-twenties. A diagnosis of possible lactose intolerance was made.
Personal habits
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Active lifestyle, walking about 3 miles, 4 days a week in her neighborhood with a walking group, bikes a local trail about 15 miles, once a week with a cycling club.
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Working full time as a nurse manager in the ER.
- •
Minimal sun exposure due to history of carcinoma, wears a wide-brim hat and UV protectant, long sleeve shirt, and sunscreen when outdoors.
- •
Avoids milk and dairy products because of her fear of lactose intolerance.
- •
Four cans of Diet Pepsi daily.
- •
Six cups of coffee daily.
- •
Does not smoke cigarettes.
- •
One glass of wine twice a week, no binge drinking.
Medication
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Probiotics.
- •
Fish oil.
- •
Calcium chew, 600 mg daily, when she remembers it: approximately once a week.
- •
Zyrtec prn for allergies.
Family history
- •
Mother had kyphosis, no fractures, deceased about 10 years ago.
Clinical examination.
- •
Weight: 154 lbs.
- •
No significant clinical findings.
DXA scan
- •
The BMD of both hips, upper 4 lumbar vertebrae, and distal nondominant radius are within the normal limits.
Laboratory investigations
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Hypocalcemia, serum calcium: 8.3, after adjusting for serum albumin.
- •
Comprehensive metabolic profile: within normal limits.
- •
Serum 25-hydroxy-vitamin D: 32 ng/mL.
Multiple choice questions
- 1.
Factors contributing to RL’s low serum calcium level include:
- A.
Lactose intolerance.
- B.
Malabsorption.
- C.
Low calcium intake.
- D.
Excessive caffeine and sodium intake.
- E.
Any of the above-mentioned possibilities.
Correct answer: E
Comment:
RL has been avoiding dairy products since her late twenties. The National Osteoporosis Foundation recommends 1200 mg of calcium daily for women over 50 years of age. She is taking 600 mg calcium chew when she remembers to take it, and probably is not getting enough calcium. In addition, she is having an excessive amount of caffeine and sodium daily. Both increase the amount of calcium lost in the urine and induce a negative calcium balance. Her serum 25-hydroxy-vitamin D level, however, is 32 ng/mL, within the normal range, and therefore not a contributing factor to her low calcium level.
- A.
- 2.
Laboratory studies recommended for RL include:
- A.
24-h urinary calcium.
- B.
24-h urinary sodium.
- C.
Ionized serum calcium.
- D.
IPTH.
- E.
All of the above.
Correct answer: E
Comment:
Assaying the 24-h urinary calcium and sodium will show if RL is losing an excessive amount of calcium via urine and this may be the etiology of her low serum calcium level. If RL is losing calcium through her urine, hydrochlorothiazide is a therapeutic management option to help her kidneys retain calcium and ultimately increase her serum calcium level.
The serum iPTH level is expected to be elevated to compensate for the low serum calcium level. A low, or low normal ionized serum calcium level is suggestive of hypoparathyroidism.
- A.
- 3.
The alternative dietary sources of calcium that RL can consume if she has lactose intolerance include:
- A.
Soy milk, almond milk, oat milk, coconut milk.
- B.
Orange juice (fortified with calcium).
- C.
Broccoli, kale, spinach.
- D.
Bread (fortified with calcium).
- E.
Any of the above.
Correct answer: E
Comment:
All of the items listed are options for lactose-intolerant patients. There are multiple other foods that can be utilized as well including almonds and sweet potatoes. Patient education is important to ensure an adequate daily calcium intake. Several foods are fortified with calcium. For instance, orange juice fortified with calcium has a similar calcium content as milk.
- A.
- 4.
Chronic calcium deficiency can cause:
- A.
Osteoporosis.
- B.
Rickets.
- C.
Osteomalacia.
- D.
Secondary hyperparathyroidism.
- E.
All of the above.
Correct answer: E
Comment:
Low calcium intake can lead to osteoporosis by decreasing bone mineral density. Calcium deficiency in children can lead to rickets. Osteomalacia is the softening of bones in adults, resulting from hypocalcemia and hypovitaminosis D.
Hypocalcemia stimulates the calcium-sensing cells in the parathyroid glands to release parathyroid hormone which stimulates bone-resorbing cells to increase the serum calcium to the normal ranges, leading to secondary hyperparathyroidism, which is characterized by an elevated parathyroid hormone level and a low or low normal serum calcium level. In primary hyperparathyroidism, both the serum calcium level and the serum parathyroid hormone level are increased.
- A.
- 5.
Symptoms of hypocalcemia include:
- A.
Neuromuscular irritability.
- B.
Renal calcification.
- C.
Depression.
- D.
Seizures.
- E.
All of the above.
Correct answer: E
Comment:
Hypocalcemia may manifest itself through a wide variety of symptoms but is usually asymptomatic especially in mild cases, as with RL. Symptoms range from neuromuscular symptoms, such as numbness and tingling of the hands and feet, to more severe ones associated with depression, cataracts, and seizures.
- A.
- 6.
RL’s 24-h urine calcium and sodium comes back:
- •
24-h calcium: 200 mEq/L normal range 100–300 mEq/L.
- •
24-h sodium: 150 mEq/L normal range 40–220 mEq/L.
Given the above results, the best course of action is:
- A.
Start a low-dose hydrochlorothiazide
- B.
Increase daily dietary calcium intake
- C.
Add 1200-mg calcium supplement
- D.
A and C
- E.
A and B
Correct answer: B
Comment:
The 24-h urinary calcium and sodium are within normal limits, meaning RL is not losing an excessive amount of calcium through her urine. She therefore probably is not ingesting enough calcium. Focusing on calcium-rich foods is the best option for RL at this stage. HCTZ can be considered if RL had hypercalciuria. Hydrochlorothiazide reduces the renal calcium excretion and has shown to reduce the fracture risk by reducing calcium lost via urinary output, and increasing the BMD.
- •
- 7.
The optimal initial treatment for RL’s low calcium level is:
- A.
Calcium citrate tablets 1200 mg daily.
- B.
Calcium carbonate tablets 1200 mg daily.
- C.
Increase dietary calcium intake 1200 mg.
- D.
Reduce sodium and caffeine intake.
- E.
C and D.
Correct answer: E
Comment:
Ideally RL should attempt to obtain calcium through dietary sources. If she is unable to do that, then she needs a calcium supplement. Calcium citrate is more easily absorbed than calcium carbonate, especially in older people who may have a low gastric acidity: reduced gastric acidity may interfere with the gastric absorption of calcium. In RL’s case, she is not taking any PPIs or H2 blockers that decrease the amount of acidity in the stomach, so she can take either supplement if needed. Also, it is important to emphasize the upper limit of calcium intake is 2000 mg/day.
- A.
- 8.
RL has increased her daily dietary calcium intake to about 1500 mg and has reduced her caffeine and sodium intake. Recheck of her calcium level is 9.0. The plan of action is:
- A.
Continue with 1200 mg of dietary calcium.
- B.
Stop efforts to increase oral calcium supplementation.
- C.
Repeat her DXA scan in 2 years.
- D.
B and C.
- E.
A, C, and D.
Correct answer: E
Comment:
RL’s dietary calcium has improved. She now needs to maintain her present increased dietary calcium intake, which can potentially increase the BMD. At present, therefore, she does not need any medication. She nevertheless needs to maintain her improved diet and increased calcium intake. Her DXA scan should be repeated in 2 years to determine if she had any changes in BMD and whether any modification or pharmacologic therapy is needed.
- A.
- 9.
Factor(s) that can interfere with dietary calcium include:
- A.
Caffeine intake.
- B.
Vitamin D level.
- C.
Malabsorption.
- D.
Sodium intake.
- E.
All of the above.
Correct answer: E
Comment:
Caffeine reduces the renal reabsorption of calcium, thus increasing the urinary calcium loss and decreasing the bioavailability of oral calcium. Caffeine also increases the urinary excretion of magnesium, sodium, and chloride.
- A.
- 10.
Medications that interact with calcium include:
- A.
Levothyroxine.
- B.
Quinolones.
- C.
Beta blockers.
- D.
Insulin.
- E.
A and B.
Correct answer: E
Comment:
Levothyroxine should not be taken within 4 h of a calcium supplement. Quinolones need a two-hour window before or after taking a calcium supplement. RL is not currently taking either medication, but it is important to keep this in mind should she be prescribed any of these tablets.
- A.
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