Introduction

Hypothyroidism is a common disorder resulting from deficiency of thyroid hormone. In areas of adequate iodine intake, autoimmune thyroid disease (Hashimoto disease, Hashimoto thyroiditis) is the most common cause of hypothyroidism. For guidelines on autoimmune thyroiditis see single organ autoimmune disease.

Thyroid-stimulating hormone (TSH) assays are the most sensitive screening tool for primary hypothyroidism. TSH levels are above the reference range, the next step is to measure free thyroxine (T4).

Results in patients with hypothyroidism are as follows:

• Elevated TSH with decreased T4 or FTI
• Elevated TSH (usually 4.5-10.0 mIU/L) with normal free T4 is considered subclinical hypothyroidism

Be aware that biotin commonly used as a supplement, interferes with hormone assays and biotin consumption should be stopped at least 2 days prior to thyroid testing.

Condition

This guideline refers to primary hypothyroidism other that of autoimmune background, i.e.:

• Iatrogenic
• caused by iodine deficiency
• congenital, when properly treated

Guidance at RECRUITMENT

ACCEPT if treated with levothyroxine (if treatment indicated) 

Guidance at CT/WORK-UP

ACCEPT, if:

• Treated with levothyroxine (if indicated).
• Asymptomatic subclinical hypothyroidism (TSH 4.5-10.0 mIU/L with normal free T4)

If anti–thyroid peroxidase (anti-TPO) and/or antithyroglobulin (anti-Tg) antibodies present refer to guidelines on autoimmune thyroiditis see single organ autoimmune disease.

DEFER if:

• Symptomatic, severe and untreated. Delay collection until treatment started and symptoms resolved.

Individual at Risk

Donor

Justification for guidance

• Myxedema coma is a severe form of hypothyroidism that most commonly occurs in individuals with undiagnosed, untreated, deep hypothyroidism who are subjected to an external stress. Donors with symptomatic hypothyroidism should therefore be deferred until treatment initiated and symptoms resolved.
• Mild/ subclinical hypothyroidism should not pose any risk for donor.

References