A 52-year-old woman comes to the office for follow-up of long-standing primary hypothyroidism, which has been treated for the past 6 years with a stable dose of levothyroxine 0.125 mg. The patient is very compliant and takes her medication an hour before breakfast every day. Recently, however, she has had increasing weight gain, dry skin, cold intolerance, and lethargy. The patient otherwise feels well and experienced menopause 6 months ago. Laboratory results at that time showed a low serum 25-hydroxyvitamin D level, which improved with oral vitamin D supplementation. She is currently taking over-the-counter calcium and vitamin D supplements every morning with breakfast. Medical history is unremarkable, and family history is positive for osteoporosis in her mother. The patient has a 35-pack-year history of smoking but quit 3 months ago with bupropion as she heard that "smoking increases the risk of bone fractures." She does not use alcohol or illicit drugs. Vital signs and physical examination are normal. Serum TSH is 9 μU/mL; it was 2.3 μU/mL a year ago. Complete blood count and basic chemistry profile are normal. Which of the following is the most appropriate advice for this patient?

Question

A 52-year-old woman comes to the office for follow-up of long-standing primary hypothyroidism, which has been treated for the past 6 years with a stable dose of levothyroxine 0.125 mg.  The patient is very compliant and takes her medication an hour before breakfast every day.  Recently, however, she has had increasing weight gain, dry skin, cold intolerance, and lethargy.  The patient otherwise feels well and experienced menopause 6 months ago.  Laboratory results at that time showed a low serum 25-hydroxyvitamin D level, which improved with oral vitamin D supplementation.  She is currently taking over-the-counter calcium and vitamin D supplements every morning with breakfast.  Medical history is unremarkable, and family history is positive for osteoporosis in her mother.  The patient has a 35-pack-year history of smoking but quit 3 months ago with bupropion as she heard that "smoking increases the risk of bone fractures."  She does not use alcohol or illicit drugs.  Vital signs and physical examination are normal.  Serum TSH is 9 μU/mL; it was 2.3 μU/mL a year ago.  Complete blood count and basic chemistry profile are normal.  Which of the following is the most appropriate advice for this patient?

Quizplus · Accepted Answer

Explanation: 11ec2b69_c13c_084f_8f63_616bb3066e68_MD0005_00 Levothyroxine has a narrow therapeutic index, and bioavailability is sensitive to a number of dietary factors. To ensure adequate and consistent absorption, levothyroxine should be administered on an empty stomach with water at least 30-60 minutes before breakfast. In addition, a number of medications, including over-the-counter drugs, interfere with the absorption of levothyroxine and must be administered at separate times to allow for proper uptake of the medication. Common offenders include calcium and iron preparations. These supplements should be separated from levothyroxine by 3-4 hours. This patient is separating levothyroxine from calcium by only an hour, which is likely leading to decreased absorption of levothyroxine and subsequent under-replacement. She should be counseled to take her calcium later in the day, and TSH should be rechecked in 6 weeks. (Choice A) Bupropion, which is often taken for up to 12 weeks as part of a smoking-cessation program, has no significant interaction with levothyroxine. (Choice C) Pregnancy and oral estrogen preparations can increase levothyroxine requirements due to increased blood levels of thyroxine-binding globulin. However, dose requirements usually do not increase after menopause and often decline with age. (Choice D) Patients with autoimmune hypothyroidism are at increased risk for other autoimmune diseases, such as celiac disease, which can, in turn, cause decreased intestinal absorption of levothyroxine. However, this patient has no gastrointestinal or skin manifestations of celiac disease, and her normal blood cell counts and response to oral vitamin D replacement make a significant malabsorptive disorder less likely. (Choice E) The patient's levothyroxine requirement was previously stable over a long period. Progression of autoimmune thyroid failure usually happens early in the course of hypothyroidism and is unlikely to be the cause of this patient's increase in TSH. Educational objective: Patients with hypothyroidism should take levothyroxine on an empty stomach with water 30-60 minutes before breakfast. Common medications, such as calcium and iron supplements, can impair the absorption of levothyroxine and should be separated from it by 3-4 hours. References: Factors affecting gastrointestinal absorption of levothyroxine: a review. (http://www.ncbi.nlm.nih.gov/pubmed/28153426)

A 52-Year-Old Woman Comes to the Office for Follow-Up of Long-Standing