Over a 3-year period, no difference in the stability of thyroid stimulating hormone (TSH) was observed between patients receiving synthetic levothyroxine vs those receiving desiccated thyroid for the management of hypothyroidism, according to the findings of a recently published retrospective matched cohort study.
The study, which was conducted at Kaiser Permanente Colorado, aimed to compare the longitudinal stability of TSH in patients taking synthetic levothyroxine vs desiccated thyroid products for the management of hypothyroidism. The study authors utilized electronic medical, pharmacy, and laboratory records to identify patients 18 years and over with hypothyroidism who received either levothyroxine or desiccated thyroid between January 1, 2005, and December 31, 2015.
Patients were matched 1:1 based on age, gender, and race/ethnicity and were followed for a 3-year period after the index date. The primary endpoint of the study was the percent of TSH values considered to be in-range (0.320-5.500uIU/mL).
A total of 870 patients were identified and included in the study. Baseline demographics showed that patients who received desiccated thyroid had a lower body mass index (P =.032), hemoglobin A1c (P =.041), and baseline TSH value (P=.001) compared with patients who received levothyroxine.
“There was no difference in the primary outcome between the 2 groups as TSH values were in-range (0.320-5.500uIU/mL) 79.3% of the time compared with 79.1% of the time for levothyroxine and desiccated thyroid patients, respectively (P = .905),” the study authors reported.
Significantly less visit-to-visit TSH variability was observed in patients prescribed levothyroxine compared with those prescribed desiccated thyroid (1.25 vs 1.44; P =.015). It was noted that 60% of patients in both treatment groups had 100% of their TSH values in range during the study period (P =.951).
The authors also reported the median number of TSH labs obtained per patient over the study period was 4 for the levothyroxine group and 3 for the desiccated thyroid group (P =.578).
According to the findings of this study, no difference was observed in the longitudinal stability of TSH between patients receiving levothyroxine compared with desiccated thyroid. “This was an unanticipated finding given concerns for variability between batches of desiccated thyroid cited by national guidelines,” the study authors stated. They concluded, “For providers targeting a tighter TSH goal in certain patients, the decreased TSH variability with levothyroxine could be clinically meaningful.”
Kuye R, Riggs C, King J, Heilmann R, Kurz D, Milchak J. Thyroid stimulating hormone stability in patients prescribed synthetic or desiccated thyroid products: a retrospective study. Ann. Fam. Med. 2020;18(5);452-454. doi.org/10.1370/afm.2545.