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q       Hyperthyroidism à Thyroid overactivity à ­­­ Free T3, T4 à Clinical syndrome / thyrotoxicosis. ???

q       20-40 years.

q       >99% are caused by intrinsic thyroid diseases, a pituitary cause is extremely rare.

Causes

          1. Grave’s disease: 80%.

          2. Solitary toxic nodule / adenoma (Plummer’s disease): 10%.

          3. Toxic multinodular goiter (rare).

¯ S-TSH, ­ T₃, T₄.

v    Grave’s disease:

q       Commonest cause.

q       Thyroid stimulating Abs = TSH receptor (IgG) Abs.

q       Associated with HLA-DR3.

q       Y. entercolitica & E. coli contain TSH binding sites which can cross-react with TSH receptor (molecular mimicry).

q       Exophthalmos, vitiligo, pretibial myxedema.

q       Associated with other organ-specific autoimmune diseases.

q       Pathology: Hyperplasia of follicles.

q       Neonatal Grave’s disease is due to transplacental transfer of thyroid stimulating IgG from mother to fetus.

Clinical Features

Treatment

1. Antithyroid drugs:

carbimazole, methimazole, propylthiouracil, b-blockers (propranolol).

2. Surgery: subtotal thyroidectomy.

Indications:

q       Big goiter.

q       Failure of medication.

q       Pregnant, children.

q       Older women who want to become pregnant.

q       Hot nodule.

Complications:

q       Hemorrhage à Respiratory obstruction.

q       Stridor:  bilateral recurrent laryngeal nerve palsy.

q       Hoarseness:

o       Local trauma.

o       Sup. Laryngeal nerve palsy (subtle change in voice).

o       Recurrent laryngeal nerve palsy.

q       Hypothyroidism.

q       Recurrent hyperthyroidism.

q       Transient hypocalcaemia:

o       If damage to one of parathyroid glands occurs.

q       Thyroid crisis:

o       Rare, mortality 10%.

o       Thyrotoxicosis, severe restlessness & tachycardia, hyperpyerxia.

3. Radioactive iodine (¹³¹I).

Iodine – ¹³¹I accumulates in thyroid & destroys gland by local radiation, though it takes several months to be fully effective.

Disadvantages:

q       Long-term: Destruction of follicular cells à No T4, T3 à Permanent hypothyroidism.

q       Avoid pregnancy for the next 6 months, because it might lead to congenital hypothyroidism.

q       Contraindicated in children & while breast-feeding as well.

Goiter (Thyroid enlargement)

          ·     Female > Male.

Clinical Features:

·     Majority are painless.

·     If esophageal / tracheal compression à can produce dysphagia & difficulty in breathing.

Investigations:

1. TFTs.

2. Chest & thoracic inlet x-rays:

          ·     To detect tracheal compression & large retrosternal extensions.

3. FNA.

4. US:

          ·     Tells whether nodules are solid / cystic.

5. Thyroid scan (¹²⁵I / ¹³¹I):  distinguish between functioning (hot) & non-functioning (cold) nodules.  

written by: Khalid Bin Yaroof. FMHS, UAE University.