Physiology
· = [Hypothalamus] > TRH > [Anterior pituitary] > TSH > [Follicular cells] > T4 & T3 > [Tissue]
[Hypothyroidism] – Starting= thyroxine treatment
· = < 60y & no IHD – Full dosage [1.6 mcg/kg] e.g. 75kg man =3D 125m= cg
· = Else – Low dose [25-50mcg]
· = Test TSH @ 6-8w
[Hypothyroidism] – Monitori= ng thyroxine treatment
· = Test TSH @ 6-8w after dose change
· = Alter dosage by 25mcg if needed
· = TSH aim
· = lower half of reference range [0.4-2.5]
· = below reference range acceptable in young patents on high dose Rx.=
· = Do not overtreat [T4 high or towards upper limit, TSH suppressed]
· = Once established, monitor anually [25% poor compliance or absorption] <= o:p>
[Hypothyroidism] – Stopping= thyroxine treatment
· = Only if transient cause suspected – stop after 6/12, recheck TFT in 6w<= o:p>
Tests
· = T3 & T4 – [Free form active] [T3 5 times more potent, 1/2 life 24h] [T4 1/2 li= ve 7d]
· = Thyroglobulin autoantibodies – [High – Graves, Hashimoto’s, De Quervains, 7% of M & 15-20% of F without disease]
· &n= bsp; Anti-TPO antibodies – [High – Hashimoto’s, idiopathic atrophy] [Low – Graves, De Quervains,= 8% M & 10% F withouth disease]
Hypothyroidism
· = Worldwide – [Iodine deficiency most common]
· = Developed nations – [Hashimotos – Autoimmune, +- Goiter, high anti-TPO antibody, low thyroglobin antibody], Chronic autoimmune thyroiditis
· &n= bsp; Other – Iatrogenic [Anti-thyroid Rx, Lithium, Amiodarone], De Quervain’= s, Silent thyroiditis (typically post partum)
· &n= bsp; Subclinic hypothyroidism [Raised TSH, Normal T4, asymptomatic]=
· &n= bsp; Repeat in 3-6/12 with anti-TPO antibodies
· &n= bsp; TSH =3D< 10
· &n= bsp; 2-5% progression to overt hypothyroidism per annum [80% overt by 4y if anti-TPO positive]
· &n= bsp; Consider Rx. if TSH rising, Goiter or trial if symptoms for 3-6/12
· &n= bsp; Else, yearly surveillance of TSH if anti-TPO positive, 3 yearly if anti= -TPO negative
· &n= bsp; If TSH > 10
· = Treat following confirmation [as high risk of progression]
Hyperthyroidism
· = 90% – [Graves – Thyroid stimulating IgG against TSH receptors & periorbital tissue] [Toxic nodular – single or multiple]<= /p>
· = 10% – Thyroiditis [De Quervain’s, Silent/post partum, Amiodarone] =
Referral criteria
· = Hypothyroidism – [<16] [pregnant or post partum] [pituitary disease] [Newborn] – consider if [active/unstable IHD] [rx. with amiodarone or lithi= um] [non responsive symptoms with adequate Rx.] [TSH persistently raised on Rx.= ]
· = Hyperthyroidism – [All]
Patient information
· = Hypothyroidsm – http://www.patient.co.uk/health/hypothyroidism-underac= tive-thyroid-leaflet
· = Advice for newly diagnosed hypothyroidism=
· = It will take at least a week after initiating therapy for the symptoms = to improve. In those with muscle weakness, stiffness, or cognitive defects that it may take up to six months= to fully resolve the symptoms.
· = There will be no noticeable effect if one dose is missed
· = Take a double dose on the day after a missed tablet (except in active ischaemic heart disease and atrial fibrillation)
· = Levothyroxine should be taken on an empty stomach to maximise absorptio= n
· = Treatment is life long.
· = When dose is adjusted, you will need a repeat blood test in 6 to 8 weeks. When dose the right do= se is found, you will need yearly measurement of TSH level -the dose may be adjus= ted accordingly.
· = In the UK, patients with hypothyroidism are eligible for a medical exemption certificate for prescription charges