Abstract:
Background. Fatigue is often the complaint that initiates thyroid function investigation. Most
available data related to fatigue and hypothyroidism involved patients with subclinical
hypothyroidism where fatigue was not the primary outcome. This study investigated the
association between TSH levels and fatigue and if there was a target TSH interval that was
associated with lower incidence of fatigue in patients with hypothyroidism.
Methods. An analytic, retrospective cohort study design assessed the relationship between TSH
levels and fatigue. All adult patients at one endocrinology clinic who were diagnosed with
hypothyroidism between January 1, 2006 and December 31, 2007 were included. Diagnoses
were confirmed by biochemical testing. Data were abstracted from the clinic’s electronic
medical record. Fatigue status was self-reported by the subject during examination by the
endocrinologist. Fatigue status and TSH levels were obtained twice: at diagnosis and during the
first follow-up visit.
Results. A total of 135 patients met the inclusion criteria. After treatment, all patients had
reductions in TSH levels. Those subjects reporting relief from fatigue tended to be males (p =
0.003), had lower TSH levels at follow-up (p < 0.001), had larger TSH differences from baseline
(p =0.007), and had a primary diagnosis of acquired hypothyroidism (p < 0.001). Females were
2.9 times more likely to report persistent fatigue than males. Patients with primary diagnosis of
thyroiditis were 3 times more likely to report persistent fatigue than those with acquired
hypothyroidism.
Conclusions. The observed relief from fatigue after treatment correlated with a higher TSH
reduction compared to patients with persistent fatigue. It was unclear if fatigue relief was related
to the level of TSH reduction (TSH difference) or to a lower absolute TSH level reached after
treatment.
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