Levothyroxine Sodium Oral Solution Normalizes Thyroid Function in a Patient with Hashimoto’s Disease, Gastritis, Diabetic Gastroparesis, and Small Intestinal Bacterial Overgrowth (SIBO)

BACKGROUND: Levothyroxine (L-T4) is used as a standard-of-care treatment in patients with hypothyroidism. L-T4 is absorbed throughout the small intestine, and consistent drug absorption is required for successful treatment. Patients with Hashimoto’s disease (autoimmune thyroiditis) often have food and medication sensitivities, as well as comorbid gastrointestinal (GI) disorders detrimental to L-T4 absorption. CASE PRESENTATION: This case report describes a 51-year-old female patient with long-standing Hashimoto’s disease and multiple sensitivities to food chemicals and medications. The patient suffered from GI symptoms and poor thyroid-stimulating hormone (TSH) control. She was switched to compounded thyroxine/triiodothyronine medication due to her multiple allergies, with only mild improvement in thyroid function and no symptom resolution. She was subsequently diagnosed with gastroparesis and small intestinal bacterial overgrowth (SIBO). Because of further worsening of her GI symptoms and weight loss, she was switched to levothyroxine sodium oral solution (Tirosint(®)-SOL), which contains only three ingredients—levothyroxine, water, and glycerol—which was well tolerated and led to normalization of TSH levels. CONCLUSION: Malabsorption of L-T4 is often seen in patients with Hashimoto’s disease-related hypothyroidism and comorbid GI conditions, such as gastroparesis and SIBO. L-T4 tablets and a compounded oral suspension were inefficiently absorbed, leading to suboptimal TSH control. Switching to levothyroxine sodium oral solution resulted in sustained TSH control with subsequent resolution of symptoms. No side effects or reactions to the medication were observed, despite the patient’s multiple allergies and sensitivities to food chemicals and medications.