Thyroid Hemiagenesis: Narrative Review and Clinical Implications.

Area of Science:

• Endocrinology
• Congenital Anomalies
• Thyroid Disorders

Background:

• Thyroid hemiagenesis (THA) is an uncommon congenital anomaly characterized by the absence of one thyroid lobe.
• It is more prevalent in females and may be linked to genetic factors and endemic hypothyroidism.
• Most cases are sporadic, but familial clusters and associations with other thyroid conditions exist.

Purpose of the Study:

• To provide a comprehensive review of thyroid hemiagenesis.
• To explore its epidemiology, etiopathogenesis, genetics, and clinical associations.
• To consolidate findings from global research on THA.

Main Methods:

• Systematic literature search of Medline, PubMed, and Embase databases.
• Inclusion of case reports, case series, and original articles published within the last 20 years.
• Analysis of data on epidemiology, associations with thyroid cancer, hyperparathyroidism, Graves' disease, Hashimoto's thyroiditis, and other congenital abnormalities.

Main Results:

• Left THA (53%) is more common than right THA (29.4%) or isthmus absence (17.6%).
• THA is associated with thyroid cancer (F:M ratio 3.25:1), hyperparathyroidism, Graves' disease (86.7% left THA), Hashimoto's thyroiditis, and other congenital abnormalities.
• Most patients with THA are asymptomatic and have normal thyroid function, though hypofunction can occur.

Conclusions:

• Thyroid hemiagenesis is a poorly understood condition often detected incidentally.
• Its clinical significance arises when remnant thyroid tissue necessitates surgical excision, leading to thyroxine supplementation.
• Further research is needed to fully elucidate the pathogenesis and optimal management of THA.