This document provides an overview of subclinical hyperthyroidism (SH), including its classification, prevalence, etiology, natural history, clinical significance, diagnosis, and treatment. SH is defined by low or undetectable thyroid stimulating hormone (TSH) levels with normal free thyroxine and triiodothyronine levels. It is classified based on TSH levels and divided into prevalence depending on factors like age and iodine intake. Causes include persistent or transient endogenous thyroid issues as well as exogenous factors like medication. While its natural history is variable, progression to overt hyperthyroidism occurs in 5% of cases. Treatment aims to restore the euthyroid state and involves confirming the diagnosis, assessing

1. Subclinical
hyperthyroidism(SH)
By Dr Mengistu Kassa
Assistant professor of General surgery
Debretabor university , Ethiopia

2. Outlines
• Introduction
• Classification
• Prevalence
• Etiology
• Natural history
• clinical segnificance
• Diagnosis
• Treatment

3. Introduction
• Low or undetectable TSH levels, with normal free
T4 and total or free T3 levels.
• Somewhat of a misnomer because the condition is
defined by biochemical characteristics, and it is
preferable to say mild thyroid dysfunction

4. Classification
Divided into two categories:
1. low but detectable TSH levels (0.1 to 0.4 mIU per
L), and
2. suppressed TSH levels (less than 0.1 mIU per L).

5. Prevalence
• Prevalence in adult population depends on age,
sex, and iodine intake
• 0.7% had suppressed TSH levels (<0.1 mU/L), and
1.8% had low TSH levels (<0.4 mU/L)
• In old patient >70 yrs(~15%)
• In pt taking thyroxine(~20%)

6. Etiology
1. Endogenous
A. Persistant
• Toxic Multinodular
Goiter
• Graves’ ddiseas
• Toxic adenoma
• Pituitary disease (Central
hypothyroidism)
B. Transient
• Subacute thyroiditis
• Silent ththyroiditi
• Postpartum thyroiditis
• Euthyroid Sick Syndrome
• Initial post-therapy period
after treatment for overt
hyperthyroidism

7. Etiology....
• Exogenous
• Iatrogenic Overtreatment with levothyroxine (most
common cause)
• Factitial thyrotoxicosis (surreptitious levothyroxine
intake)
• Drug-induced thyroiditis (amiodarone, α-IFN)
• Iodide excess (radiographic contrasts)
• TSH-lowering medications (steroids, dopamine)

8. Natural History
• Is variable
• over all progression rate to overt hyperthyroidism is
5%
• Factors affecting the natural history include the
degree of TSH suppression and the etiology

9. Clinical significance SH
• Cardiovascular disease
• Tachycardia, atrial fibrillation, increased left
ventricular mass index, increased cardiac
contractility, impaired endothelial function,
reduced exercise tolerance, reduced heart rate
variability
• Milder and less frequent than, those of overt
hyperthyroidism
• Risk was greater in subjects with TSH levels <0.1
mU/L

10. • Osteoporosis and fractures
• Influenced by the duration of the disease,
associated risk factors for bone loss, and degree of
TSH suppression
• Changes induced by the thyroid hormones???

11. Diagnosis

13. Management
• Aim of therapy is to restore the euthyroid state and
avoid potential side effects
• Involves the following 6 steps:
• 1) confirmation,
• 2) assessment of severity,
• 3) determination of the cause,
• 4) assessment of potential cocomplications
• 5) evaluation of the necessity of treatment, and
• 6) selection of the most convenient therapy_x0000_

14. • Therapeutic strategies vary depending on 3 key
factors
• 1) cause,
• 2) severity, and
• 3) associated morbidity.

15. Before starting treatment
• Patients at high risk of complications from SH, TSH
and free T4 should be repeated within 2–6 weeks
• For all other patients, it is important to document
that SH is a persistent problem by repeating the
serum TSH at 3–6 months, prior to initiating
therapy.

16. Principle of treatment
Factor TSH (<0.1 mU/L) TSH (0.1–0.4 mU/L)
Age >65 years Treat Consider treating
Age <65 years with
comorbidities(Heart
disease ,Osteoporosis
Menopausal, not on
estrogens or
bisphosphonates &
Hyperthyroid symptoms)
Treat Consider treating
Age <65 years,
asymptomatic
Consider treating Observe

17. Election of Treatment
• The armamentarium of treatment is similar for overt and
subclinical disease
Thionamides
• Mild Grave's disease in young patient
• To make pt euthyroid before surgery or radioiodine therapy
Surgery
• Young individuals with a single hyperfunctioning nodule (toxic
adenoma) and toxic multinodular goiter
• Graves’ disease if medical therapy fails
Radioiodine
• For old patient with MNG and cardiac disease

18. Referance
• William's Text Book of endocrinology 14th ed
• Americal thyroid association guidline
• International journal of endocrinology
• Europian thyroid association guidline