Hyperthyroidism

Hyperthyroidism

·        Symptoms: ¯weight, appetite­, frequent stools, tremor, irritability, hot intolerance, sweating, oligomenorrhoea, infertility

·        Signs: Tachycardia, AF, warm peripheries, thyroid enlargement or nodules

·        Additional signs in Grave‟s disease: exophthalmos (bulging eyes), lid lag (lid lags eye when following your finger descending slowly), vitiligo (growing patches of skin depigmentation due to ¯melanocytes), Pretibial Myxoedema (due to amyloid)

·        Tests:

o   Progression: 

§  TSH is suppressed first, while fT3 and fT4 normal Þ TSH is the most sensitive test. Suppresses with minor changes in fT4

§  fT3 rises next ® mild symptoms

§  fT4 rises last ® severe symptoms

o   Screening: fT4 and TSH

o   Severity: fT4 and fT3

o   Thyroid microsomal and thyroglobulin antibodies (only present in 80% of Graves at presentation)

o   If goitre, ultrasound, thyroid scan

o   Test visual fields, acuity and eye movements.  Referral if positive.  Steroids to reduce swelling

·        Causes:

o   Grave‟s disease: F:M = 9:1.

§  Most common when < 50 (­ multinodular goitre as you get older)

§  Probably results from Autoantibodies against TSH receptors. Check for hTSABs (human Thyroid stimulating antibodies)

§  May cause normochromic, normocytic anaemia, ­ESR, ­calcium, abnormal LFTs 

§  Histology: large hyperchromatic nuclei, retracted thyroglobulin. Follicles same as in follicular carcinoma but carcinoma shows invasion of blood vessels

o   Toxic adenoma (= Plummer‟s Disease, Thyroid autonomy): a nodule producing T3 or T4 ® hot spot on scan

o   Subacute Thyroiditis:

§  = De Quervain‟s Disease. Usually resolves in 3 – 6 months. If rapidly destructive then acute thyroiditis

§  = Inflammation of the thyroid secondary to:

·        Pregnancy: autoimmune.  Gland may not be tender

·        Infection: coxaxyvirus and mumps.  Tender gland

§  Goitre (often painful).  Usually self-limiting

§  If severe, then 3 phases:

·        Prodromal: may be 4 – 6 weeks longs

·        Hyperthyroid: Release of preformed T3 and T4. TSH low. If very bad, fT4 will be 100 (normal = 10 – 24). ­ESR in parallel with ­T4

·        Hypothyroid/regenerating: For 2 weeks – 2 months. In proportion to severity of hyperthyroid phase. T3 and T4 will go very low (?gland exhausted), TSH will remain depressed for a while longer (ie resembles secondary failure)

§  Doesn‟t respond to carbimazole as it‟s releasing preformed hormone. Carbimazole stops formation of hormone. If mild then wait. If severe, then antagonise peripheral effects (eg propranolol). Steroids work but prolong illness

§  Histology:

·        Neutrophils attack cuboidal epithelium (acute inflammation)

·        Thyroglobulin leaks out ® granuloma formation

·        Resolution

o  Post-partum thyroiditis: hyper or hypo thyroid.  Hypothyroid may persist

o  Other: Toxic Multinodular Goitre, self medication (­T4 but ¯T3), follicular carcinoma of thyroid

·        Treatment:

o  Drugs: Thyourylenes: Carbimazole (40 mg/day PO for 4 weeks, then reducing every 1 – 2 months, withdraw after 18 months, 50% relapse) – or try block and replace strategy (ongoing carbimazole and replacement T4), propylthiouracil. Risk of agranulocytosis with Carbimazole and propylthiouracil

o  Toxic multi-nodular goitre and toxic adenoma unlikely to remit following drugs

o  Partial thyroidectomy: risk to recurrent laryngeal and parathyroids. May be hypo or hyper post surgery

o  Radioactive iodine (I131): will ultimately become hypothyroid