THYROID GLAND

PACTICAL ACTIVITY NO. 5

Morphofunctional investigations of the thyroid

1. In vitro methods:1.1. Basal hormone determinations1.2. Dinamic tests1.3. Other specific laboratory findings

2. In vivo methods:2.1. Radioactive iodine uptake: RAIU(thyroid Tc-uptake)2.2. Thyroid scintigraphy: TSG2.3. Thyroid ultrasound2.4. Fine-needle aspiration biopsy: FNAB

3. Nonspecific investigations

1. In vitro investigations1.1. Basal hormonal assessments:TSHfT4, FT4 - free-T4; total T4 fT3, FT3 - free T3; total T3

A. Serum TSH: normal range: 0.5-4.5 mIU/L Diagnostical value (interpretation of pathological values): TSH : primary hypothyroidism (subclinical or overt form) TSH-secreting pituitary adenoma Refetoff syndrome (thyroid hormone resistance) TSH : hyperthyroidism central hypothyroidism systemic illness Dopamine or glucocorticoid administrationDuring systemic illness normal or fT4 with TSH in the acute phase and in the recovery phase.Dopamine or glucocorticoid administration TSH , normal fT4 and fT3.

B. Serum free-T4 (fT4, FT4)normal range: 0.8-2 ng/dL or 0.7-2.5 ng/dL 9-30 pmol/LDiagnostical value (interpretation of pathological values): fT4 : overt hyperthyroidism TSH-secreting pituitary adenomafT4 : overt hypothyroidism (primary or central) Refetoff syndrome

C. Serum T3 or free-T3:normal range: 0,5-1,5 ng/mL or 0,2 0,5 ng/dL 3-8 pmol/L Diagnostical value only in hyperthyroidism:fT3 and fT4 : overt hyperthyroidism fT3 and fT4 normal: overt hyperthyroidism with T3

Thyroid function testing algorithmTSHlowfT4fT4Normal, fT4 normal higheuthyroid statelowNhighlowNhighCentral hypo-thyroidism Subclin. hyper-thyroidismOvert hyper-thyroidismTSH-secreting pituitary adenoma/ Resitance to TH Subclin. primary hypo-thyroidismOvert primary hypo-thyroidism

1.2. Dinamic tests

TRH stimulation test TSH stimulation test (Queridos test) T3 suppression test (Werners test) A. TRH stimulation test- TRH 200-400 g iv. - TSH measure at 0, 20, 30, 60Interpretation: N: stimulated TSH 7mIU/L exaggerated response: I. hypothyroidism exaggerated response, but tardive and prolonged: III hypothyr.- low or absent response: II. hypothyroidism or high thyroid hormone levels: hyperthyroidism or exogenous thyroid hormones.

B. TSH stimulation test (Queridos test):1. utility:- fT4, T3, RAIU at 24 hours before the test- 10 IU TSH im/day few days, than fT4, T3, RAIU- to differentiate I. from II. hypothyroidism2. utility:- associated with thyroid scintigraphy (TSG)- Interpretation: to show the presence of inhibited thyroid tissue on TSG in case of thyroid autonomy.- rarely used

1.3. Other specific laboratory findings

Antithyroid antibodies:- TSH-receptor antibody: TRAb- anti-thyroid peroxidase antibody: ATPO- anti-thyroglobulin antibody: aTg

Thyroglobulin (TG):- to show the remnant thyroid tissue or recurrence (in thyroid bed or metastases) in case of thyroid cancer after total thyroidectomy- differential diagnosis between hyperthyroidism (TG) and exogenous thyroid hormone in excess (TG )- diagnostic value in congenital myxedema (TG )

Tumor markers:- TG (in thyroid cancer, see above)- calcitonin: normal range < 1.5 ng/L, high in MTC- nonspecific tumormarker: ACE carcinoembryonic ag. (MTC)

2. In vivo investigations:2.1. Radioactive iodine uptake: RAIU determines the intrathyroidal iodine turnover a jeun 10 Ci I131 or 40 Ci I123 RIAU normal range:I123 : 6h = 5-15% 24h= 8-30% I131 : 2h= 20 5% 24h= 40 5% 48h= lower with 5-15% to the value at 24hTc99m: 0.5-3%RIAU : hyperthyroidism iodine-deficient goiterRIAU : acompanying thyroiditis thyroid hormone administration iodine exposure hypothyroidism, lack of thyroid tissue

2.2. Thyroid scintigraphy: TSG

morphofunctional investigation of the thyroidIndications: thyroid nodules, retrosternal goiter, ectopic thyroid tissue (ex. mediastinal), congenital malformations, postoperative recurrence

Terms: - thyroid nodules: - isofunctional nodule- hyperfunctional or hot nodule high uptake- hypofunctional or cold nodule low or absent uptake - compensated autonomous thyroid adenoma - decompensated autonomous thyroid adenoma

Contraindications:- pregnancy, nursing mother- 6 months before conception- suckling, infancy - only for I131

TSG normal imagiesTSG with I131TSG with Tc99m

TSG with I131 thyroid autonomyJapanese flag aspect decompensated autonomous adenoma, hot nodule with a cold part, surrounded by the inhibited thyroid tissue

TSG with Tc99m - toxic thyroid adenomaHot nodul in the right lobe, inhibited intact thyroid tissue decompensated autonomous adenoma aspect of Japanese flag

T3suppression test (Werner): T375-100g in divided doses daily for 5 days it reduces the 24-hour RAIU by more than 50% the iodide uptake in the unaffected surrounding thyroid tissue will disappear

Compensated autonomous adenoma

A. Norgmal TSG B. Cold nodule C. Hot noduleD. Multihetero-nodular goiterTSG with Tc99mMultinodular toxic goiter

2.3. Thyroid ultrasound

Normal aspect: homogenous, isoechoic structure

Thyroid nodules

Hashimotos thyroiditis

PET CT Elastography

2.4. FNAB Fine-needle aspiration biopsy- elective method to differentiate benign and malignant thyroid nodules- in outpatient unit, without local anaesthesia- 25 G or 27G needle FNAB results:- benign: about 70 % out of results; - malignant: 1- 5 %; - suspected, follicular lesion: 11-13%; - inadequate, non-diagnostic: 11-13%. The sensibility and specificity is 90%.