IntroduceIntroduceR. GholamnezhadR. Gholamnezhad

Lecturer of school of nursing & midwifery of IranLecturer of school of nursing & midwifery of Iran university

Ph D t d t f I l S h l f di lPh.D student of Immunology, School of medical sciences of Isfahan university

E-Mail: Gholami278@gmail. Com 

InterpretingInterpretingof of

thyroid function teststhyroid function tests

ScopeScope

• The detection of thyroid dysfunction in adults (individuals 19 years of age and over) 

• Monitoring adult patients treated for thyroidMonitoring adult patients treated for thyroid function disorders.

ScopeScope• Routine thyroid function testing is notRoutine thyroid function testing is notrecommended in asymptomatic adults.However testing may be indicated when non‐However, testing may be indicated when nonspecific signs and symptoms are present inpatients at risk for thyroid diseasepatients at risk for thyroid disease

Risk factors for thyroid diseaseRisk factors for thyroid disease

personal history of thyroid disease

strong family history of thyroid disease 

diagnosis of autoimmune disease

past history of neck irradiation 

drug therapies such as lithium and amiodarone

women over age 50

elderly patientsy p

women 6 weeks to 6 months post‐partum 

Diagnosis/Investigation

Hypothyroidism Hyperthyroidism

•Weight gain•Hair loss•LethargyM t l i l iti ( h i )

•Weight loss•Hair loss•Palpitations / Tachycardia / Atrial fib ill ti•Menstrual irregularities (menorrhagia)

•Cognitive impairment•Depression•Constipation

fibrillation•Menstrual irregularities (amenorrhea / oligomenorrhea)•Widened pulse pressurep

•Goitre•Dry skin•Cold intolerance

p p•Nervousness and tremor•Muscular weakness•Goitre•Heat intolerance diaphoresis clammy•Heat intolerance, diaphoresis, clammy hands•Hypertension

pointpoint• Measurement of TSH has become theMeasurement of TSH has become theprincipal test for the evaluation of thyroidfunction in most circumstances A TSH valuefunction in most circumstances. A TSH valuewithin the reference interval excludesmajority of cases of primary overt thyroidmajority of cases of primary overt thyroiddisease. If TSH is abnormal, confirm thediagnosis with free T4 (fT4)diagnosis with free T4 (fT4)

InterpretingInterpretingofof

thyroidfunctionteststhyroidfunctiontests

HPT AxisHPT Axis

NormalNormal

TSH =  5 mu/LTSH = 0/4 – 4/5 mu/LT3 = 87‐ 180 ng/dl

T4 = 5/6 13/7 mcg/dl

T3 T4 TSH

T4 = 5/6 – 13/7 mcg/dlFT3= 230 – 420 Pg /dlFT4 = 0/8 – 1/5 ng/dl

HyperthyroidismHyperthyroidism

T3T4

TSH

HypothyroidismHypothyroidism

TSH

T3T4

Please before sampling NOTE:Please before sampling NOTE:You do not have to fast but because of the influence ofYou do not have to fast, but because of the influence ofturbidity caused by eating fat on the test results, at least3 hours before the test, do not eat food.

Up to 2 weeks after surgery to avoid these tests.

Use of contraceptive pills can increase the hormones.

Concentration of thyroid hormones in the summer is20% lower than winter.Sampling is not done between 16‐18 hours.

1•Common causes:Primary hyperthyroidism ‐ Graves' disease, multinodular goitre, toxic nodule.

Relatively common causes with low radio‐iodine uptake:Transient thyroiditis (postpartum, post‐viral, De Quervain'sthyroiditis).

Rare with a low radio‐iodine uptake:Thyroxine ingestion.•Ectopic thyroid tissue.

Low TSH Raised FT3 or FT4

p y•Iodine‐induced.•Amiodarone therapy.

Rare with a positive pregnancy test:Rare with a positive pregnancy test:Gestational thyrotoxicosis with hyperemesis  gravidarum.•Hydatiform mole.

Rare:Familial TSH receptor mutation.

22•Common causes:•Common causes:Subclinical hyperthyroidism.•Thyroxine ingestion.

•Rare causes:Low TSH Normal FT3 

or FT4

Rare causes:Steroid therapy.•Dopamine and dobutamine infusion.•Non‐thyroidal illness.

33C•Common causes:Non‐thyroidal illness.•Recent treatment for hyperthyroidism.

Rare causes:Low TSH Low FT3 or 

FT4

Rare causes:Pituitary disease.•Congenital TSH or TRH deficiencies

4Common causes:Chronic autoimmune thyroiditis.•Following radio‐iodine.g•Following thyroidectomy.•Transient thyroiditis ‐ hypothyroid phase.

Rare causes (anti‐TPO negative):Following external beam radiotherapy to the neck.•Drugs ‐ amiodarone, lithium, interferons, interleukin‐2.

Raised TSH

Low FT4 or FT3

•Iodine deficiency.

Congenital causes:Congenital causes:Thyroid dysgenesis.•Iodine transport defects.•TSH‐receptor defects.•TSH resistance.

55Common causes:Subclinical autoimmune hypothyroidism.

Rare causes:Drugs ‐ amiodarone, sertraline, colestyramine.•Recovery phase after non‐thyroidal illness.

Raised TSH

Normal FT3 or FT4

y p y•Heterophile (interfering) antibody.

Congenital causes:Congenital causes:TSH‐receptor defects.•TSH resistance

66• Rare causes:

Amiodarone.• Interfering antibodies.

F ili l• Familial.• TSH‐secreting pituitary tumour.• Acute psychiatric illness

Normal or Raised TSH

Raised FT3 or FT4

T k ☺Thank you ☺y