Introduction: Many causes of malabsorbtion of levothyroxine (LT4) in patients with hypothyroidism have been thoroughly described in literature. Pseudomalabsorption, poor compliance of the patient is most common cause of failure of LT4 and/or liothyronine (LT3) treatment.
Case report: 27 years old woman, normopondeal, presented from the age of 11 years for short stature. Further investigations found pluritrope pituitary insufficiency (somatotrophic, gonadotroph, corticotroph and tireotroph) and substitutive treatment was started (GH-treated off 17 years, actual height 168 cm, cortisol, esoprogestative and thyroid hormones). MRI described a small pituitary. Despite of increasing dose of LT4, ulterior in association with LT3, and vitamic C for better absorption, THS remained high (13 μUI/ml, reference 0.44 mU/L) with constantly low fT4. Celiac disease, pernicious anemia, gastrointestinal, liver, pancreatic, heart disease or pregnancy were excluded by laboratory and imagistic investigations, also were excluded drugs and dietary interactions; To evaluate the hypothesis of pseudomalabsorption, the patent was submitted to rapid LT4 absorption test. After an overnight fasting, it was administreted 1000 μg LT4; We measured fT4 at 30′, 2, 4, 6 h.Immediately fT4 serum increase, with the maximum serum level after 2 h (basal fT4=0.56 ng/dl, 2 h=1.72 ng/dl, peak fT4>2.5). The test showed a normal absorption of LT4 and malabsorption was excluded.
Conclussion: Our case showed an inadequate thyroid hormone supplementation (3.3 μg/kg); the literature suggested that after excluding organic cause or drug interaction, is useful to make a malabsorption test, which confirms the diagnostic pseudomalabsorption; based on his historical attempts to stop the treatment, a psychological counseling may be necessary. Once weekly oral thyroxine treatment, supervised, can be a safe, well-tolerated, and effective therapy for patients with non-compliance.
20 - 23 May 2017
European Society of Endocrinology