Abstract
Background:
There is a scarcity of data on thyroid function abnormality in coronavirus disease 2019 (COVID-19) outpatients in the world literature since previous studies were done on admitted patients.
Aim:
The objective of this study was to assess thyroid function tests (TFT) in Libyan outpatients with COVID-19 as well as the possible association between them and some routine hematological, inflammatory and biochemical markers.
Methods:
Laboratory results were retrospectively reviewed for a total number of 246 patients, where 214 patients with laboratory-confirmed COVID-19 and 32 non-COVID-19 patients were included in the study as a control group. The majority of the patients were females 179 (72.8%) and age range between 18 and 88 years old. They were registered in the outpatient department of COVID-19 at Zaweit-Dahmany Polyclinic in Tripoli, Libya between May and October 2021. Serum levels of thyroid-stimulating hormone (TSH), thyroid hormones (THs) (triiodothyronine (T3), thyroxine (T4), and free fractions), complete blood count (CBC), C-reactive protein (CRP), lactate dehydrogenase (LDH), liver function test (LFT), and renal function test (RFT) were measured.
Results:
Abnormal thyroid function was seen in 17.8% of 214 patients with COVID-19. Twelve patients had isolated low total or free triiodothyronine (FT3), suggestive of nonthyroidal illness syndrome (NTIS), ten patients had hypothyroidism that was subclinical in six patients and overt in the remaining four patients. Three patients had hyperthyroidism. Thirteen patients had different isolated THs abnormalities. Low FT3 was associated with older age (P= 0.035), and it has a weak negative correlation with CRP (-0.335) and LDH (-0.245) (P= 0.001). The thyroid dysfunction (TD) group presented a statistically significant reduction in lymphocytes (P= 0.000), increased neutrophil (P= 0.000), increased CRP (P= 0.000), increased urea (P= 0.014), increased alkaline phosphatase (ALP) (P= 0.007), a slight reduction in hematocrit (HCT) (P= 0.010), low mean corpuscular volume (MCV) (P= 0.019), and low mean corpuscular hemoglobin (MCH) (P= 0.019) but no significant difference in hemoglobin (Hb), red blood cells (RBC), white blood cells (WBC), and platelet count when compared to euthyroid control.
Conclusion:
Clinicians should be vigilant about the possible presence of thyroid function abnormalities among COVID-19 patients, especially elderly patients, and those with increased inflammatory markers.

Key words: COVID-19, Thyroid dysfunction, Biochemical markers, Inflammatory markers, Hematological markers