Background: Thyroid dysfunction is one of the common abnormalities encountered in contemporary clinical endocrinology practice. There is a fairly wide spectrum of thyroid dysfunction which can be identified by patterns of thyroid function test results. Whereas overt hypothyroidism or hyperthyroidism are clinically manifest and can be distinguished by the pattern of changes in serum T4, T3 and TSH levels, subclinical thyroid dysfunctions are essentially laboratory-based diagnoses. Objective: To describe the spectrum (pattern and prevalence) of thyroid dysfunction among patients evaluated by thyroid function tests at a tertiary clinical laboratory. Method: The study was a retrospective study that was carried out by retrieving and reviewing archived thyroid function tests results stored in an electronic database of a fully-automated tertiary clinical laboratory. Results: Among the results, 68.8% indicated euthyriodism while thyroid dysfunction occurred in 31.2% of cases. The spectrum of thyroid dysfunction included: primary hyperthyroidism (13.7%), subclinical hypothyroidism (6.3%), primary hypothyroidism (4.9%), subclinical hyperthyroidism (4.1%), euthyriod sick syndrome (1.5%) and euthyriod hyperthyroxinaemia (0.3%). Primary and subclinical hyperthyroidism were more common in females while primary and subclinical hypothyroidism were more common in males. Conclusion: Thyroid dysfunction is a fairly common endocrine abnormality in our contemporary clinical practice and it occurs in a wide range of spectrum. Primary hyperthyroidism is the most common form of thyroid dysfunction in our environment with women of child-bearing age being the mostly affected.