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Thyroid gland
- two lateral lobes joined by isthmus
- Weight 10-20 g
- Microscopy: several follicles containing colloid and surrounded by
a single layer of epithelium
- Follicle cells produce thyroglobulin – stored as colloid
- Thyroid gland secretes thyroxine –T4, triodothyronin T3
Physiologic effects of thyroid hormones
Cardiovascular effects: increased heart rate, output
GIT: increased motility
Skeletal: bone turnover
Neuromuscular: increased protein turnover, speed of muscle
contraction
Metabolism: gluconeogenesis, glycogenolysis, lipolysis
Sympathetic NS: increased numbers of beta-adrenergic receptors in
heart, increased CAT activity
Thyroid evaluation
Functional status: euthyroid, hyperthyroid, hypothyroid
Structural abnormalities
Volume
Thyroid autoantibodies
FNAB – fine needle aspiration biopsy
Thyroid evaluation
Hormones: total T3, T4 – measures total hromones binding to protein –
can be changed due to changes of plasma proteins
-pregnancy etc.
-Free T4,T3 – more exact measurement of thyroid function
-TSH
-Thyroglobulin: follow up of patients with papillary or follicular cancer ( less
then 10 ug/l)
-Calcitonin: assessment of medullary ca
Thyroid evluation
Thyroid imaging:
1. Ultrasound: volume, cystic nodules, solid nodules, autoimmune
thyroiditis
2. 123I or 99mTechnecium scintigraphy: hot and cold nodules
after thyroidectomy
FNAB: cytology: carcinoma, cysts, autoimmune thyroid.
Thyroid Ab: TPO, anti TG, anti TSH-r : autoimmune disease
Hyperthyroidism
-clinical syndrome resulting from elevated T-hormones.
Causes: Graves disease, toxic adenoma,toxic multinodular goiter,
subacute thyroiditis, Hashimoto, postpartum thyroiditis
Iodine induced: contrast media (X ray), amiodarone
History:
Symptoms: nervousness, sweating, heat intolerance, palpitation,
fatigue, weight loss, tachycardia, dyspnea, weakness, increased
apetite, eye complaints, diarrhea, amenorrhea
Hyperthyroidism
Physical examination:
Hot skin, tachycardia, goiter, tremor, eye signs, atrial fibrilation,
splenomegaly
Thyrotoxic crisis: thyroid storm – can be precipitated by surgery,
Iodine, stress, amiodarone
Signs: fever, tachycardia, arrhythmias, sweating, cardiac failure., rarely
coma. Vomiting, diarrhea.
Hyperthyroidism
Graves disease: common cause – autoimmune
More common in women (peak 20-40 years)
Signs: goiter, tachycardia, exophtalmos, dermopathy –
myxedema
Hyperthyroidism
Eye signs: inflammatory infiltrate of orbital tissue,
periorbital edema, conjunctival congestion, proptosis,
optic nerve damage
Pretibial myxedema
Laboratory findings: elevated FT3, FT4, decreased
TSH
Anti TSH-r, ATPO, aTG
MRI, US of orbits.
Treatment
1. Antithyroid drugs: metimasol, carbimasol, PTU :
duration of 6-12 months
Definitive treatment:
1. Radioactive iodine: final therapy
2. Surgery: total thyroidectomy – Graves disease,
lobectomy – nodular toxic goiter
Hypothyroidism
Definition: clinical syndrome due to deficiency of
thyroid hormones
Infants and children: retardation of growth and
development – mental retardation – cretinism
Causes: congenital: agenesis, dysgenesis,
dyshormonogenesis
Adult onset: autoimmune (Hashimoto), thyroidectomy,
iodine therapy
Hypothyroidism
Secondary: hypothalamic
pituitary – adenoma, pituitary surgery,
idiopathic, RAT
Clinical symptoms:
History: fatigue, cold intolerance, weakness, lethargy,
weight gain, constipation, myalgias, arthralgias,
menstrual irregularities, hair loss
Hypothyroidism
Physical examination – signs:
Dry, cold skin, bradylalia, brittle nails, peripheral edema, delayed
reflexes, slow reaction time, bradycardia, pleural or pericardial
effusion.
Laboratory tests:
Decreased FT3, FT4, increased TSH – primary hypothyroidism,
decreased FT3, FT4, TSH- secondary
anti TG, anti TPO – autoimmune
Cholesterol, TG, CK, anemia,
Treatment
Synthetic L-thyroxine – replacement therapy
Average dose: 100-150 ug/day
Monitored by serum TSH – 1-3 mIU/l.
Myxedema coma: L- thyroxine i.v., Hydrocortisone
Secondary: L thyroxine after hydrocortisone replacement
Goiter
Enlargement of thyroid gland
- euthyroid, hyper or hypothyroid
- Causes: inadequate hormonogenesis, iodine
deficiency, autoimmune thyroiditis, dietary goitrogens-cabbage
- Diffuse, nodular, multinodular
- Evaluation: function, morphology
Goiter-management
Treatment:
Surgery
L-thyroxine – suppression – leads to TSH suppression
US
Scintigraphy
CT, MRI
FNAB
Thyroiditis
Acute
Subacute
chronic
Acute:
suppurative – bacterial
Signs: Fever, septicaemia, redness, tenderness.
FNA: identifying bacteria
Treatment: antibiotics, surgery
Thyroiditis
Subacute (De Quervain)
Inflammatory, viral infection
Fever, neck pain, signs of thyrotoxicosis
Laboratory:SR, CRP, FT4,FT3
US: typical picture.
FNAB: large multinuclear cells
Treatment: NSAD, corticosteroids
Thyroiditis
Chronic (Hashimoto)
Lymphocytic thyroiditis
- resulting in hypothyroidism
- Symptoms: Goiter, hypothyroidism
- Examinations: aTG, aTPO
- US: typical picture
- FNAB: lymphocytic infiltration
- Treatment: L thyroxin – if hypothyroidism
Thyroid carcinoma
1. Papillary: well differentiated – good prognosis
metastases only into lymph nodes
2. Follicular: differentiated: good prognosis, metastases: lymph
nodes, bones, lung
3. Anaplastic: non differentiated: poor prognosis
4. Medullary – more malignant, part of MEN 2, produces calcitonin
5. Lymphoma - rare
Investigations: US, CT, scintigraphy, FNAB
thyroglobulin, calcitonin
Thyroid carcinoma - treatment
1. Surgery – total thyroidectomy
subtotal or lobectomy – in small less trhan 1 cm
2. Suppressive and replacement therapy – L thyroxine
3. Radio iodine
4. Anaplastic – chemotherapy
5. Medullary: total thyreoidectomy, radiotherapy