Differentiation Between Clinical and Subclinical Hypothyroidism in Pathophysiology, Symptoms, Diagnosis and Treatment – A Narrative Review

Mustafa Mohammed Albassam; Noor Mohammed Obaid; Yasser Kadhim Hashem Al-Zwaini

doi:10.47419/bjbabs.v5i03.285

Authors

Mustafa Mohammed Albassam College of Pharmacy, Al-Esraa University, Baghdad , Iraq https://orcid.org/0000-0003-0338-5615
Noor Mohammed Obaid College of Pharmacy, Al-Esraa University, Baghdad , Iraq https://orcid.org/0000-0002-9859-6687
Yasser Kadhim Hashem Al-Zwaini College of Pharmacy, Al-Esraa University, Baghdad, Iraq https://orcid.org/0000-0003-0195-0238

DOI:

https://doi.org/10.47419/bjbabs.v5i03.285

Keywords:

Clinical Hypothyroidism, Levothyroxine, Liothyronine, Subclinical Hypothyroidism

Abstract

Subclinical hypothyroidism is characterized by elevated thyroid-stimulating hormone (TSH) levels with normal serum free thyroxine (fT4) and free triiodothyronine (fT3) concentrations. In contrast, overt primary hypothyroidism occurs when fT4 levels fall below the normal reference range. Diagnosing subclinical hypothyroidism is challenging due to varying upper limits of normal for TSH. This review explores the differentiation between clinical and subclinical hypothyroidism in pathophysiology, symptoms, diagnosis, and treatment.

Overt hypothyroidism lacks a singular identifying symptom, while subclinical hypothyroidism is often asymptomatic. However, both conditions can present with non-specific symptoms such as mild to moderate weight gain, fatigue, impaired concentration, depressive symptoms, and menstrual irregularities. These symptoms alone are insufficient for diagnosis, necessitating thyroid function tests for confirmation.

Levothyroxine (LT4) is the primary treatment for hypothyroidism and is one of the most widely prescribed medications worldwide. LT4 has a slower onset of action and produces prolonged effects compared to endogenous thyroid hormones. It facilitates the conversion of thyroxine (T4) to triiodothyronine (T3) and normalizes TSH levels, replenishing the body's T3 reserves. While LT4 monotherapy is the standard treatment, a combination of LT4 and Liothyronine (LT3) may be considered for hypothyroid patients. However, some evidence suggests that T3 levels may not be fully restored in patients receiving LT4 therapy alone. The choice of treatment should be individualized based on clinical presentation, symptom severity, and laboratory findings.

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