Case 2: In Sickle Cell Disease, Endocrine Dysfunction May Signal Iron Overload

Frequent blood transfusions are necessary in sickle cell disease to manage chronic— often severe—anemia. Chronic transfusions can lead to iron overload, manifestations that may appear indirectly as endocrine function disorders, such as hypothyroidism. Testing, however, can reveal the underlying cause.

Initial Presentation

Nancy A. is an African-American woman 32 years of age, married, mother of two young daughters, and currently unemployed. She has SS genotype sickle cell disease (SCD). She presented to a sickle cell center for a follow-up visit with complaints of extreme fatigue and intermittent pain in her back and shins that had persisted for the past 3 days. Her pain was reported as 5/10 on the linear pain scale (0 = no pain, 10 = excruciating pain).

Diagnosis and Treatment

Nancy was diagnosed with chronic anemia due to hemolysis of the sickled red cells. Intermittent blood transfusions might be required if her hemoglobin fell 2 g/dL below her baseline, which is 8 g/dL. A blood test yielded these results: hemoglobin 8.6 g/dL; hematocrit 24.9%; white blood count 12.2 mcg/L; reticulocyte count 9.4%; thyroid-stimulating hormone (TSH) 6.56 mIU/L; ferritin 3226.0 mcg/L (which was high); mean corpuscular volume 106.2 fL; and fetal hemoglobin 15.7%.

Nancy was scheduled for a thyroid ultrasound to check for thyroid nodules. Because of her high serum ferritin, she was placed on daily chelation therapy with deferasirox 1500 mg daily (based on 20 mg/kg—the minimum approved initial dosage with the maximum efficacy and the fewest side effects). With deferasirox, the dosage can be increased to 25 mg/kg to 30 mg/kg over time (3-6 months) if a patient shows no response to therapy; 40 mg/kg is the maximum approved dosage.

Nancy underwent ophthalmic and auditory exams prior to starting deferasirox, as ocular and aural disturbances have been reported with deferasirox usage. She was taught how to adhere to the medication regimen. She was advised that deferasirox may cause stomach upset, nausea, and diarrhea, but that by increasing fiber in her diet, these side effects may be lessened. She was educated on the importance of tracking her transfusions and units of red blood cells transfused, and of adhering to monthly follow-up visits for laboratory tests to monitor her ferritin, kidney and liver functions, and complete blood count. She was given a personal medical record booklet to note her test results and advised to bring it with her to each doctor visit.

Follow-Up

Nancy received a thyroid ultrasound that revealed mild thyromegaly but no thyroid nodules. Her ophthalmic and auditory exams were normal. She continues with daily deferasirox therapy and has monthly tests to monitor her ferritin and TSH levels. Her most recent ferritin level was 2644.0 mcg/L (normal range is 13.0 mcg/L-150 mcg/L); her TSH level was 4.90 mIU/L (normal range is 0.27 mIU/L-4.2 mIU/L). As is typical with patients with SCD who have chronic transfusional iron overload, chelation therapy with deferasirox is initiated whenever Nancy's ferritin levels reach >1000 mcg/L; patients with ferritin levels of 500 mcg/L to 1000 mcg/L should be educated about iron overload and monitored. With Nancy, this is an ongoing process.

Discussion

Iron overload affects such endocrine organs as the thyroid gland, pancreas, ovaries, testes, liver, and pituitary gland, as well as the heart and brain. Early signs of hypothyroidism, diabetes, and menstrual disorders may be related to iron overload in patients with SCD. Nurses should be alert for such signs and target patients who are at risk.

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