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