Lithium Induced Hypothyroidism

Question 1

What is it?

Answer 1

A raised TSH and normal T4 is consistent with subclinical hypothyroidism (a raised TSH and reduced T4 is overt hypothyroidism). Lithium is a recognised cause of this.

Subclinical hypothyroidism lacks the classic features of hypothyroidism (hence subclinical) but is sometimes associated with subtle neuropsychiatric symptoms such as lethargy, mental slowing, and depression.

Due to a lack of research in this area management is controversial. That being said the guidance suggests that if the patient is asymptomatic and the TSH < 0.1 mu/l then management should consist of monitoring only and the bloods should be repeated a month later and then 3 monthly. Conversely if the TSH > 0.1 mu/l or the patient is symptomatic then thyroxine should be given.

Propylthiouracil and carbimazole are treatments for hyperthyroidism.

Question 2

Management

Answer 2

Due to a lack of research in this area management is controversial. That being said the guidance suggests that if the patient is asymptomatic and the TSH < 0.1 mu/l then management should consist of monitoring only and the bloods should be repeated a month later and then 3 monthly. Conversely if the TSH > 0.1 mu/l or the patient is symptomatic then thyroxine should be given.

Propylthiouracil and carbimazole are treatments for hyperthyroidism.