Hypothyroidism laboratory findings

Hypothyroidism Main page
Patient Information
Overview
Classification Primary hypothyroidism Hashimoto's thyroiditis Secondary hypothyroidism Tertiary hypothyroidism
Differentiating different causes of hypothyroidism
Screening
Diagnosis
History and symptoms

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Overview

To diagnose primary hypothyroidism, many doctors simply measure the amount of Thyroid-stimulating hormone (TSH) being produced. High levels of TSH indicate that the thyroid is not producing sufficient levels of Thyroid hormone (mainly as thyroxine (T4) and smaller amounts of triiodothyronine (fT3)).

Laboratory Findings

Electrolyte and Biomarker Studies

Although TSH levels can detect primary hypothyroidism, measuring just TSH fails to diagnose secondary and tertiary forms of hypothyroidism, thus leading to the following suggested blood testing if the TSH is normal and hypothyroidism is still suspected:

• thyroid-stimulating hormone (TSH)
• free triiodothyronine (fT3)
• free levothyroxine (fT4)
• total T3
• total T4

Additionally, the following measurements may be needed:

• antithyroid antibodies - for evidence of autoimmune diseases that may be damaging the thyroid gland
• serum cholesterol - which may be elevated in hypothyroidism
• prolactin - as a widely available test of pituitary function
• testing for anemia, including ferritin