What is the average age of onset for hypothyroidism?

Average Age of Onset of Hypothyroidism

The average age of onset for hypothyroidism is approximately 60-65 years, with the condition becoming progressively more common with advancing age, particularly in women. 1

Age-Specific Onset Data

Primary Hypothyroidism in Older Adults

• In a large study of 655 patients with hypothyroidism, the mean age at diagnosis was 61.8 years in men and 59.8 years in women 1
• The prevalence of hypothyroidism increases substantially with age, affecting up to 20% of women older than 60 years 2
• In the general US adult population without known thyroid disease, subclinical hypothyroidism affects 4-8.5% of adults overall, but increases to 20% in women over age 60 2

Gender and Ethnic Differences

• Hypothyroidism shows less female predominance in certain populations (such as those with 22q11.2 deletion syndrome), where onset occurs on average decades earlier than general population expectations 2
• The prevalence in blacks is one-third that in whites, suggesting ethnic variation in age of onset 2
• In men older than 65 years, the prevalence increases and approaches that of women in some studies 2

Age-Related Considerations

Subclinical Hypothyroidism Prevalence by Age

• Approximately 12% of persons aged 80 years or older with no evidence of thyroid disease have TSH levels greater than 4.5 mIU/L, indicating that the reference range for TSH shifts upward with advancing age 3
• The median TSH level tends to increase with advancing age, particularly in individuals over 80 years old 3

Progression Rates

• Patients with subclinical hypothyroidism progress to overt hypothyroidism at a rate of approximately 2-5% per year 2, 4
• The rate of progression is proportional to the baseline serum TSH concentration and is higher in individuals with antithyroid antibodies 2

Etiology by Age Group

In patients older than 55 years with hypothyroidism, the causes are distributed as follows 1:

• Autoimmune thyroiditis: 47.0% (most common cause)
• Postoperative hypothyroidism: 26.7%
• Therapy for previous thyrotoxicosis: 9.6%
• Unknown etiology: 13.1%

Special Population: 22q11.2 Deletion Syndrome

• Nearly 1 in 4 adults with 22q11.2DS require treatment for primary hypothyroidism, with onset on average decades earlier than general population expectations 2
• Onset is often in adolescence or young adulthood in this population 2

Clinical Implications of Age at Onset

Treatment Considerations in Older Adults

• Older patients require lower doses of levothyroxine than younger patients to normalize TSH levels 5
• Doses of 100 micrograms per day or less were common in patients over age 40, and some patients over age 60 needed only 50 micrograms per day or less 5
• The daily dose of thyroxine needed to lower serum TSH into the normal range was significantly less in older patients than in younger ones 5