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Hypothyroidism – A clinical state 
due to underproduction 
of thyroid hormones .PRIMARY HYPO-
( > 95 % )

TSH high
T3 low or normal
T4 low

. Problem is in the gland – ie gland failure due to
♦ damage
♦ inhibition
♦ removal of gland itself. Iodine deficiency- worldwide commonest cause. Autoimmune thyroiditis- most common cause- Hashimoto thyroiditis Atrophic thyroiditis 
( Primary Myxoedema ) May happen with or without goitre Atrophic autoimmune thyroiditis . Post-ablative therapy or surgery- Thyroidoectomy Radioactive Iodine External radiotherapy. drugs – Anti-thyroid drugs- about 15 % people will develop hypothyroidism 10-20 yrs after treatment
♦ Carbimazole
♦ Propylthiouracil Amiodarone Lithium Interferons Thalidomide Rifampicin. Transient 
thyroiditis-  Subacute thyroiditis 
( de Quervain’s ) Postpartum thyroiditis- within 6/12 post partum. Infiltration Thyroid hypoplasia /agenesis – Tumour , amyloidosis , sarcoidosis , haemochromatosis , TB and scleroderma. Congenital -Absence or underdevelopment of the thyroid gland , ectopic hypoplastic gland or enzyme defect

Overt-TSH above normal reference range
♦ usually above 10
♦ FT4 is below the normal reference range May not be symptomatic In Pregnancy- TSH > 10 is overt hypothyroidism
 regardless of T4

Subclinical- Raised TSH but FT4 and FT3 normal Clinical features of hypothyroidism usually absent , but if present -related to degree of TSH elevation TPO antibodies help define the risk of developing overt hypothyroidism Repeat test in 3-6 mts time ( exclude transient causes of ↑ in TSH )

( < 5 % ) 

Low T4
TSH low / normal or slightly raised. Pituitary- Pituitary dysfunction- Tumours ( adenoma ) Surgery , radiotherapy or trauma Infarction Sheehan’s synd Infiltrative disorders Isolated TSH deficiency or inactivity

Hypothamamic dysfunction
Often also mentioned as tertiary hypothyroidism in literature Tumours ( eg glioma ) Surgery , radiotherapy or trauma Infiltrative disorders Idiopathic hypothalamic dis Drugs ( eg retinoids )

How common- Prevalence 1-2 % in the UK More common in women ( up to 10 times ) One of the most common chronic disorders Secondary hypothyroidism is rare A major cause of 1 ary hypothyroidism in the developing world is Iodine deficiency Primary hypothyroidism – management is straightforward → mostly done in primary care with thyroxine replacement

See chart for presentation Symptoms may be vague subtle and non-specific – reputation as mimicker Progressive fatigue and malaise Myalgia arthlagias and paraesthesias Symptoms may be insidious developing over yrs Elderly may be asymptomatic

Myxedema coma -also known as myxedema is the rare but deadly manifestation of severe hypothyroidism high mortality rate presents with hypothermia ( as low as 23° ), coma and seizures

Risk factors- Iodine deficiency Family h/o thyroid or autoimmune disorders Middle age Female sex ↑ common in whites compared to other races and ethnicities Pre-existing other autoimmune illnesses as type 1 diabetes
rheumatoid arthritis
multiple sclerosis
Coeliac disease
Addison’s disease
pernicious anaemia
vitiligo Previous treatment with radioactive iodine or radiation to upper neck/ chest H/O thyroid surgery Down’s and Turner’s syndrome Bi-polar disorder Primary pulmonary hypertension Amiodarone use Lithium use

Complications – Dyslipidemia CAD and stroke Heart failure Impaired fertility Pregnancy- miscarriage , anaemia , pre-eclampsia , placental abruption , PPH , stillbirth Adverse neo-natal outcomes

Clinical symptoms – Slow , dry haired ,thick skinned , deep voiced patient with weight gain , cold intolerance , bradycardia and constipation
( classical presentation ) Diffuse hair loss from scalp and eyebrows Most cases present with non-specific symptoms Poor memory or general intellectual deterioration Usually picked up on biochemical testing Delayed relaxation phase of Achilles’s jerk

Investigations – Dyslipidemia- improves with treatment FBC- mild normocytic anaemia Fasting blood glucose may be elevated Muscle enzymes e.g CK may be elevated Consider cortisol 
(exclude co-existent Addison’s disease ) Hyponatraemia in severe cases Thyroid antibodies – antithyroid peroxidase antibodies elevated in 90 % of patients with autoimmune thyroiditis ECG- bradycardia , low voltage complexes

Treatment -All symptomatic patients with Primary hypothyroidism-Levothyroxine – synthetic compound
 identical to T4 converted to T3 in extrathyroidal tissue 1/2 life of 7 days Single dose 1/2 an hr to an hr before breakfast-Cause of hypothyroidism Age of the patient Co-existing heart disease Usual dose to achieve full replacement is between 100 µg to 150 µg

TSH level is used to assess response
( other than people with pituitary disease ) It take atleast 2 months ( 6-8 weeks ) for the pituitary-thyroid axis to re-set after introducing treatment or a dose adjustment Aim of the treatment is to 
◘ make the patient feel better
◘ normalise serum TSH
◘ avoid over-treatment

Referral –Age less than 16 Pregnant or post-partum Subacute thyroiditis Goitre , Nodule or structural change in thyroid gland Suspected of having associated endocrine disease
♦ Do not start thyroxine replacement if suspected adrenal 
failure → can precipitate adrenal crisis Newborn infant Particular management problems 
♦ IHD or pre-existing cardiac disease
♦ Treatment with amiodarone or Lithium
♦ adverse effects from treatment -If worse after starting Rx → suspect Addison’s disease Female and planning pregnancy Atypical or misleading thyroid functions Persistently raised TSH despite adequate treatment after excluding
♦ poor adherence
♦ drug interactions
♦ malabsorption Persistent symptoms despite treatment e ,g > 200 µcg of treatment and compliant with treatment.



Printable 2 page leaflet from American Thyroid Association  – print and hand out for patients to read- short summary very concise and useful- 

A page for all thyroid-related problems from ATA- has information on all and any aspect related to the thyroid gland

Leaflets available from British Thyroid Foundation– choose and print pdf version

An excellent 8 page resource can be printed from National Institute of Diabetes and Digestive and Kidney Diseases

Thyroid UK printable pdf on hypothyroidism and treatment

Levothyroxine patient information from Medicine compendium

A rare patient information source for subclinical hypothyroidism from healthline


NICE draft on Thyroid disease: assessment and management June 2019

Management of primary hypothyroidism : statement by the British Thyroid AssociationExecutive Committee Clinical Endocrinology 2015

Liothyronine ( L-T3 ) information from BTF

ATA professional guidelines

from the above – ATA hypothyroidism section is available on

Getting confused with TFTs ? read this article from Australian prescriber. com by Prof Mortimer

Another valuable information leaflet from Camden Clinical Commissioning group


  1. CKS NHS hypothyroidism
  2. BMJ Best practice Hypothyroidism
  3. Clinical Review Management of hypothyroidism in adults BMJ 2008 ; 337 ;a801
  4. Hypothyroidism – Causes , Killers and Life-Saving Treatments Sarah B Dubbs MS et al Emerg Med Clin N Am 32 ( 2014 ) 3030-317
  5. Management of Hypothyroidism in Adults Nikhil Tandon Supplement to JAPI January 2011 Vol 59
  6. Clinical Examination E-Book – Owen Epstein Kumar and Clark’s Clinical Medicine Abnormal TFT Results NHS Guidance Camden Clinical Commissioning 


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