7370 Review of the Literature, and Report of a Series of Patients with Lactose Intolerance and Levothyroxine Malabsorption in Treatment with Liquid L-T4

Abstract Disclosure: S. Ferrari: None. A. Patrizio: None. V. Mazzi: None. F. Ragusa: None. C. Botrini: None. G. Elia: None. E. Balestri: None. E. Barozzi: None. L. Rugani: None. F. Bracchitta: None. G. Stoppini: None. G. Frenzilli: None. E. Baldini: None. C. Virili: None. S. Benvenga: None. P. Fallahi: None. A. Antonelli: None. Intolerance to lactose-containing foods is frequent, with a prevalence of 7-20% in Caucasians, and of 80-95% among Native Americans. Therefore, lactose intolerance (LI) issue needs to be taken in account in the management of hypothyroid patients needing large doses of levothyroxine (L-T4) (> 1.7-2 μg/kg/day) to achieve euthyroidism. Indeed, the absorption of oral T4 may be affected in patients with LI, by following a diet containing lactose, whereas it is resulted to be improved with a lactose-free diet. Lactose is often present as a supplementary ingredient in many commercially available drugs, as L-T4 preparations. In susceptible individuals, drugs containing lactose can cause LI symptoms, and lactose in L-T4 preparations could impair thyroxine absorption. Moreover, it has been shown that patients with LI requiring an increased dosage of L-T4 benefit from a treatment with a lactose-free L-T4 formulation. The lactose-free liquid L-T4 formulation is able to circumvent LI malabsorption leading to the normalization of thyroid-stimulating hormone (TSH) in patients with subclinical hypothyroidism, and long term stable TSH levels. Further studies will be needed to evaluate the liquid L-T4 formulation in larger numbers of patients with hypothyroidism and LI. Presentation: 6/3/2024