Worsening Hypothyroidism and Multiple Nutrient Deficiencies Following Gastric Bypass: The Importance of Close Monitoring   

Preethi Krishnan, MD; Beena Sattar, MD; Lekshmi Dharmarajan, MD 

Introduction:

The increasing prevalence of obesity in the U.S. has resulted in an increase in gastric bypass procedures with dramatic weight loss and patient satisfaction. Though surgical management of obesity has been proven to be effective in reducing obesity-related comorbidties, along with the weight loss, several undesired consequences including nutritional deficiencies may occur.

 

The following case illustrates a 53 year old female who underwent sleeve gastrectomy (2006) and Roux-enY gastric bypass (RYGB) in 2007 followed by marked weight reduction; not anticipated were the subsequent complications including worsening hypothyroidism and multiple vitamin deficiencies.

 

The Case:

53 year old female, known case of primary hypothyroidism since 1989, on levothyroxine (225 mgms /d), was hospitalized with fatigue, fall and slow heart rate. She had been taking levothyroxine in the range of 200-250 mcg/day; medications also included calcium supplements, iron, multivitamins and esomeprazole. Initial evaluation: BP 110/69 mm Hg, heart rate 45/min, normal temperature. She was monitored in the ICU for arrhythmia. Her TSH values were 35.6 in 2005, 40.2 in 2006 (prior to sleeve gastrectomy) and 0.062 in Sept 2007 prior to the Roux-enY procedure.  The BMI was 42 in 11/2006 prior to the bariatric procedure.

 

Laboratory investigations  at this admission: TSH 67 IU/ml (0.35-4.8), Free T4-0.3 ng/dl (0.9-1.9), B12: 197 pg/ml (200-700), MCV 100 fl, 25 Hydroxy Vit D level (total D2 +D3):12 ng/ml (20-100), calcium: 6.9-7.4 mg/dl (8-10), PTH: 200 pg/ml (10-65), magnesium: 1.4-.1.6 mg/dl (1.6-2.5), Phosphorus: 2.3-2.5 mg/dl (2.7-4.5) and parietal cell antibody positive.

 

On admission she was mildly dehydrated with lab values consistent with hemoconcentration (Hb 12.5g/dl and Hct 35.5%, baseline Hb/Hct 10/31); elevated serum creatinine (1.2 mg/dL) and BUN of 19 mg/dL normalized with IV hydration. .The dehydration was attributed to poor oral intake.

 

The patient was placed on IV levothyroxine and her pulse improved to 55-58/min. She was discharged home on levothyroxine 150mcg/daily, calcium carbonate 650mg 2 tabs bid, ferrous sulfate 325 mg tab bid and B12 injections, with advice to follow up at endocrine clinic. Vitamin D levels were only available post –discharge. The patient was consuming all her medications (including levothyroxine) at the same time.

 

Discussion:

Nutritional deficiencies are common in patients after bariatric procedures, especially   iron, calcium and vitamin B12, over time. It is essential to monitor patients closely for these deficiencies. The lack of gastric acid interferes with absorption of iron, B12 and calcium.

 

Further thyroid hormone is best taken half to an hour before breakfast; absorption is decreased by calcium carbonate and ferrous sulfate. Levothyroxine and other medications are to be taken 4 hours apart. Gastric bypass by itself has also been reported to improve hypothyroid state. It is likely that erratic intake of medications caused failure of absorption of thyroid hormone and worsening of hypothyroidism along with development of other nutritional deficiencies. The severe hypothyroid state responded to intravenous thyroid hormone replacement, further confirming that oral absorption of thyroid hormone even in a dose of 200 -250 mcg daily proved insufficient due to poor absorption. Bradycardia from severe hypothyroid state along with dehydration and nutrient deficiency likely contributed to the fall.

 

Conclusions:

  • The pharmacokinetics of levothyroxine and bioavailability in particular can be impaired based on the manner in which the medication is taken; levothyroxine is best absorbed in an empty stomach and is not to be taken with other medications
  • The gastric bypass procedure probably caused further alteration in absorption of thyroid hormone as also other nutrients: iron, calcium and vitamin D.
  • Following gastric by pass procedures it is important to follow patients for nutrient deficiencies, as shown here; they invariably occur with time