Lessons learnt from a case of missed central hypothyroidism

Area of Science:

• Endocrinology
• Internal Medicine
• Clinical Biochemistry

Background:

• A 57-year-old female with a history of Grave's thyrotoxicosis and partial thyroidectomy experienced a 20-year diagnostic delay for central hypothyroidism.
• The patient presented with multiple, unexplained symptoms including impaired renal function, elevated creatine kinase (CK), myositis, and pericardial effusion.

Purpose of the Study:

• To highlight the diagnostic challenges and clinical consequences of relying solely on TSH in suspected hypothyroidism.
• To emphasize the necessity of measuring free T3 and free T4 in specific clinical scenarios.

Main Methods:

• Case report detailing a patient's complex medical history and diagnostic journey.
• Review of biochemical and clinical data, including thyroid function tests (TSH, fT4, fT3), renal function (eGFR), and CK levels.
• Clinical assessment and specialist investigations for myositis and pericardial effusion.

Main Results:

• Profound central hypothyroidism was diagnosed when free T4 and free T3 were measured, despite repeatedly normal TSH levels.
• Levothyroxine replacement therapy led to the resolution of renal impairment, elevated CK, myositis symptoms, breathlessness, and pericardial effusion.
• Thyroid hormone levels normalized within one year of initiating Levothyroxine treatment.

Conclusions:

• Central hypothyroidism can occur irrespective of prior thyroid disorders and may present with normal TSH.
• Measuring free T3 and free T4 is crucial when clinical suspicion of hypothyroidism persists despite normal TSH.
• Routine thyroid function testing is recommended for patients with renal impairment or elevated CK.