For 60% of patients in both groups, TSH levels were within reference range for whole study
In the study, Dr. Kuye and colleagues matched patients (average age, 63 years; 90% women) in terms of characteristics such as race, comorbidities, and cholesterol levels.
Patients were excluded if they had been prescribed more than one agent for the treatment of hypothyroidism or if they had comorbid conditions, including a history of thyroid cancer or other related comorbidities, as well as pregnancy.
With respect to visit-to-visit TSH level variability, the lower rate among patients prescribed levothyroxine in comparison with patients prescribed desiccated thyroid was statistically significant (1.25 vs. 1.44; P = .015). Among 60% of patients in both groups, all TSH values measured during the study period were within reference ranges, however (P = .951).
The median number of TSH laboratory studies obtained during the study was four in the synthetic levothyroxine group and three for patients prescribed desiccated thyroid (P = .578).
There were some notable differences between the groups. Patients in the desiccated thyroid group had lower body mass index (P = .032), hemoglobin A1c levels (P = .041), and lower baseline TSH values (2.4 vs. 3.4 uIU/mL; P = .001). compared with those prescribed levothyroxine.
Limitations include the fact that the authors could not account for potentially important variables such as rates of adherence, differences in prescriber practice between agents, or the concurrent use of other medications.
Subjective outcomes not assessed: “One-size-fits-all approach doesn’t work”
The authors note they were not able to assess subjective outcomes, which, as noted by the editorialists, are particularly important in hypothyroidism.
“Emerging evidence shows that for many patients, symptoms persist despite normal TSH values,” Dr. Schneiderhan and Dr. Zick write.
They cite as an example a large study that found significant impairment in psychological well-being among patients treated with thyroxine replacement, despite their achieving normal TSH levels.
In addition, synthetic levothyroxine is associated with other uncertainties, such as complexities in the conversion of T4 to triiodothyronine (T3) that may disrupt thyroid metabolism in some patients.
In addition, there are differences in the amounts of thyroid replacement needed by certain groups, such as patients who have undergone thyroidectomies.
“The one-size-fits-all approach for treating hypothyroidism does not work ... for all patients,” they concluded.
The study authors and editorialists have disclosed no relevant financial relationships.
A version of this article originally appeared on Medscape.com.