Synthetic Medication, Desiccated Thyroid Similar in Effectiveness for Hypothyroidism

New research from a team at Kaiser Permanente Colorado suggests concern over impact of synthetic medication versus desiccated thyroid products on thyroid-stimulating hormone (TSH) stability when choosing hypothyroidism treatment is not warranted.

A retrospective matched cohort study with more than 800 patients, investigators found no difference in longitudinal TSH stability over a 3-year period between desiccated thyroid products and synthetic levothyroxine.

While hypothyroidism is among the most common thyroid disorders and synthetic levothyroxine is the most popular treatment for this, some clinicians prefer to treat with desiccated thyroid products. In an effort to evaluate how treatment choice could influence TSH in patients, investigators designed their study using data from electronic medical, pharmacy, and laboratory records within Kaiser Permanente Colorado.

For their study, investigators included patients aged 18 years and older receiving levothyroxine for hypothyroidism from 2005-2015. After identifying these patients, investigators matched them in a 1:1 ratio based on age, sex, and race/ethnicity to patients prescribed desiccated thyroid products.

Of note, patients were excluded if they had panhypopituitarism, were post-radioiodine therapy, had a history of thyroid cancer, were pregnant, diagnosed with Graves’ disease, or had Hashimoto’s thyroiditis. Additionally, patients were excluded if they were prescribed more than 1 agent for treatment of hypothyroidism.

For the purpose of the study, investigators chose the percent of euthyroid (0.320-5.500 uIU/mL) TSH values. Investigators also included visit-to-visit TSH variability, the percentage of patients with TSH values in-range during the follow-up period, and number of TSH values as secondary outcomes.

In total, 870 patients were included in the study. Compared to those prescribed levothyroxine, patients prescribed desiccated thyroid products had lower body mass index (P=.032), HbA1c (P=.041), and baseline TSH value (P=.001) compared with those prescribed levothyroxine. Upon analysis, investigators found no difference in TSH values time in-range between the study arms, with rates of 79.3% for levothyroxine and 79.1% for desiccated thyroid products (P=.905).

Results suggest those receiving levothyroxine had significantly less visit-to-visit TSH variability than those prescribed desiccated thyroid (1.25 vs 1.44; P=.015), but investigators noted 60% of the patients in both groups had all of their TSH values measured during the study period considered in-range (P=.951). Investigators also pointed out the median number of TSH laboratory values obtained during the study period was 4 among patients receiving levothyroxine compared to 3 for patterns prescribed desiccated thyroid products (P=.578).

In an accompanying editorial, Jill Schneiderhan, MD and Suzanna Zick, MD, both of the University of Michigan Medical School, urge clinicians to use a patient-centered approach instead of relying primarily on laboratory results when determining the effective management strategy for patients with hypothyroidism.

“Keeping desiccated thyroid medications as an option in our tool kit will allow for improved shared decision making, while allowing for patient preference, and offer an option for those patients who remain symptomatic on levothyroxine monotherapy,” wrote the pair of University of Michigan physicians.

This study, “Thyroid Stimulating Hormone Stability in Patients Prescribed Synthetic or Desiccated Thyroid Products: A Retrospective Study,” was published in the Annals of Family Medicine.