Hypothyroidism

Last updated 20.09.12

 

Index

 

Definition

-  Underproduction of thyroid hormone T4 +/- T3

 

Features

-  1o = decrease production by thyroid

-  2o = decrease production of TSH by pituitary or of TRH by hypothalamus

 

Causes

-  Hashimotos Thyroiditis

-  Most common in Aus

-  Iodine deficiency

-  Most common cause worldwide

-  Cretinism (congenital hypothyroidism)

-  Iodine excess

-  Post-partum thyroiditis

-  10% pregnant women

-  Subacute thyroiditis

-  DeQuervans thyroiditis

-  Drugs

-  Amiodarone

-  Lithium

-  INF alpha

-  Thalidomide

-  Iatrogenic

-  Radioactive iodine

-  Thyroidectomy

-  Neck irradiation

-  Sheehans syndrome (PPH)

-  Pituitary adenoma

-  Hypothalamic tumour

 

Associated S/S

-  Goitre

-  Thyroid Nodule

-  Cold intolerance

-  Decreased sweating

-  Coarse skin, hair loss

-  Muscle/joint pain

-  Myxoedema

-  OSA (macroglossia)

-  Carpal tunnel syndrome

-  Myxoedema Coma

-  Altered mental state

-  Hypothermia

-  Bradycardia

-  Hypercabia

-  Hyponatraemia

-  +/- cardiomyopathy

-  +/- pericardial effusion

-  +/- cardiogenic shock

-  +/- ascities

-  Galactorrhoea, menstrual changes

-  Fatigue, weight gain, weakness

-  Anaemia

-  Depression

-  Poor concentration, pseudo-dementia

-  Infertility

-  Constipation

-  AID (Thyrogastric cluster): Pernicious anaemia

-  Anaesthetic risk: altered drug metabolism, oedematous airway

 

Ix

-  TSH

-  Most sens screen for 1o hypothyroidism

-  If increased: hypothyroidism --> test FT4

-  FT4: decreased: hypothyroidism

-  TBG (Thyroid Binding Globulin)

-  Antithyroid Antibodies

-  Anti-TPO: Hashimotos

-  10-15% negative

-  Thyroid US: nodule, goitre

-  If nodule --> FNA

-  +/- U&E: Hyponatraemia (Myxoedema coma)

-  FBE: Anaemia

-  Lipids: often elevated

-  B12: Pernicious anaemia (AID)

-  Mx as per cause

-  +/- T4 (Thyroxine)

 

Mx

-  Thyroid Diesease in Pregnancy