Clinical Thyroid Disease Flashcards
what are the three types of hypothyroidism?
primary
subclinical
secondary
what is the difference between the 3 types of hypothyroidism?
Primary (Thyroid): Raised TSH, Low FT4 & FT3 Subclinical (Compensated): Raised TSH: Normal FT4 & FT3 Secondary (Pituitary): Low TSH, Low FT4 & FT3
what are the causes of primary hypothyroidism?
Congenital
Developmental
agenesis / maldevelopment
Dyshormonogenesis
trapping / organification / dehalogenase
Acquired Autoimmune thyroid disease Hashimotos / atrophic Iatrogenic postoperative / post- radioactive iodine External RT for head and neck cancers antithyroid drugs, Amiodarone, Lithium, Interferon Chronic iodine deficiency Post-subacute thyroiditis Post partum thyroiditis
Pituitary / hypothalamic damage pituitary tumour eg tumour craniopharyngioma post pituitary surgery or radiotherapy Sheehan’s syndrome isolated TRH deficiency
what are the investigations of hypothyroidism?
TSH / fT4
Autoantibodies: TPO (Thyroid peroxidase antibodies)
what is the treatment of hypothyroidism?
Levothyroxine (T4) tablets
(Liothyronine (T3))
Combination of T4 & T3: no benefit in studies
Initial dose Levothyroxine 50mcg/day, increase after 2 weeks to 100mcg
Increase dose until TSH normal (or fT4 in normal range in secondary)
Half-life of T4 is 7 days
After stabilisation annual testing of TSH
Compliance
what is subclinical hypothyroidism?
Consider treatment TSH > 10
TSH > 5 with positive thyroid antibodies
TSH elevated with symptoms
Trial of therapy for 3 to 4 months and continue if symptomatic improvement
what are the risks for treatment in subclinical hypothyroidism
osteopenia and atrial fibrillation
what is the effect of pregnancy on hypothyroidism
Increased Levothyroxine requirements during pregnancy
Optimise preconceptually
Inadequately treated hypothyroidism linked with increased foetal loss and Lower IQ
At diagnoses of pregnancy
Increase LT4 dose by about 25% and monitor closely
Aim to keep TSH in low normal range (<2.5mU/l) and FT4 in high normal range
Treat subclinical hypothyroidism if planning pregnancy (or pregnant)
what are the causes of Goitre?
Physiological Puberty Pregnancy Autoimmune Graves’ disease Hashimoto’s disease Thyroiditis Acute (de Quervain’s ) Chronic fibrotic (Reidel’s) Iodine deficiency (endemic goitre) Dyshormogenesis Goitrogens
what are goitre types?
Multinodular Goitre
Diffuse goitre
Colloid
Simple
Cysts
Tumours
Adenomas
Carcinoma
Lymphoma
Miscellaneous
Sarcoidosis, Tuberculosis
what are solitary thyroid nodule investigations?
Thyroid function test
(solitary toxic nodule)
Ultrasound: useful in differentiating benign vs malignant
Fine needle aspiration (FNA)
Isoptope scanning if low TSH: Hot nodule
what is the management of thyroid cancer?
Near Total Thyroidectomy High dose radioiodine (Ablative) Long term suppressive doses of thyroxine Followup Thyroglobulin Whole body iodine scanning (following 2-4 weeks of thyroxine withdrawal or recombinant TSH injections)
how do tumours arise from medullary thyroid cancer?
Tumour arise from parafollicular C cells
what is the treatment for edullary thyroid cancer?
Total thyroidectomy. No role for radioiodine
causes of thyrotoxicosis?
Primary Grave’s disease (70%) Toxic Multinodular Goitre (20%) Toxic adenoma Secondary Pituitary adenoma secreting TSH Thyrotoxicosis without hyperthyroidism Destructive thyroiditis (post-partum, subacute [de Quervain’s], amiodarone-induced Excessive thyroxine administration
