Laboratory assesment of thyroid gland function Vladimír Soška Department of Clinical Biochemistry Thyroid diseases • 90 % endocrinopathies • 5-7 % population of CR Women 4-6 x more frequently • Hypothyroidism, hyperthyroidism Primary (periferal) Secondary (central) T4 - thyroxine • Prohormone (ineffective)  Deiodination to T3 in tissues • Bound to proteins - 99,95 %  Thyroxin binding globulin, albumin, prealbumine • Total T4 - no clinical relevant  Depends on protein concentration  tT4 - not measured • fT4 - free thyroxin - biologically active T3 • Active hormon 80 % of T3 rise by deiodination from T4 in periferal tissues 20 % - thyroid gland 99,8 % is bound to proteins (TBG, albumin, PA) • tT3 (total T3) - may be measured ? • fT3 (free T3) - biologically active Better predictive value than tT3 Regulation of thyroid hormones secretion thyroid gland periferal tissues adenohypophysis hypothalamus deiodination TSH • Relationship between the level of fT4 and secretion of TSH  Logarithmic-linear • ↓ f T4 by 50 % → ↑ TSH 160x !! • TSH = the most sensitive test for detection thyroid gland dysfunction! • TSH is primary laboratory test for detection of thyreopathy Laboratory analysis • TSH • tT4 - total T4 • fT4 - free T4 • (tT3 - total T3) • fT3 - free T3 • Anti TPO • Anti TG • TRAb; • TBG  Thyroxin bind globulin • Ioduria • Thyreoglobulin • Calcitonin free T4 measurement - indication • If an ↑ or ↓ of TSH To confirm hyper- or hypothyreoidism • Monitoring the effect of treatment Free T3 measurement - indication • Diagnosis of T3 thyreotoxicosis • Dg. of subclinical primary hyperthyroidism • Unsuitable for Dg. hypothyroidism Delayed reaction Mild ↓ Up to quarter of population ! Other diseases (non-thyroidal) - syndrome of low T3 Monitoring of treatment • TG (thyreoglobuline) Ca. of thyroid gland • Calcitonin Medullary ca. of t.g. • Ioduria - supply of iodine in the body ↓ = marked iodopenia Tumor markers Antibodies • Anti TPO Thyroperoxidase antibodies Antimicrosomal antibodies • TRAb TSH-receptors stimulating antibodies TGI - thyroid growth IG Anti TG Thyroglobulin antibodies Hashimoto´s thyroiditis Graves´- Basedow thyrotoxicosis Functional testing of t. g. • TRH stimulating test  200 µg TRH i.v. TSH determination after 20 min. (2 - 25 mU/l) • Indication Subclinical hyperthyroidism Insufficient increase of TSH Changes of TSH non-thyroid • ↑ TSH Convalescence • ↓ TSH Acute diseases Fever, MI, trauma, surgery, ….. Chronic diseases Tu, DM, CHF, nefrotic sy, malnutrition Mental illness Akute, chronic Usually normal level fT4 Reference ranges • TSH (0,3 - 4,2 mU/l) • fT4 (9 - 25 pmol/l) • fT3 (3 - 6 pmol/l) tT3 (1,3 - 3,1 nmol/l) • TBG (12-30 mg/l) • Ioduria (> 100 ug/l) • TG (0 - 55 ug/l) • Calcitonin (do 150 ng/l) Primary hypothyroidism Secondary hypothyroidism Subclinical primary hypothyroidism Normal thyroid function Subclinical primary hyperthyroidism (T3-thyreotoxikóza) Secondary hyperthyroidism Primary hyperthyroidism (doplnit fT3) ↓fT4fT4normal↑fT4 ↓ TSHTSH normal↑ TSH Laboratory testing of the adrenal cortex gland function Vladimír Soška Department of Clinical Biochemistry Adrenal cortex - structure and function • 3 zones (glomerulosa, fasciculata, reticularis) • 2 functional units Independently controlled, express different enzymes Zona glomerulosa Aldosteron Controlled by - renin, angiotensin system Zona fasciculata, zona reticularis Glucocorticoids Androgens (testosteron), a little amount of oestrogens Controlled by ACTH Cortisol (hydrocortisone) • Synthesis control Negative feedback ↓ cortisol = ↑ CRH, ↑ ACTH ↑ cortisol = ↓ CRH, ↓ ACTH Stress Hypoglycaemia Circadian rhythm • Metabolism Binding to prot. (90 %) Transcortin Urinary excretion Cortisol 17-OH-steroids Circadian rhythm of cortisol • Basal value - 8 h. morning M: 250-650 nmol/L; F: 140-740 nmol/L • Afternoon - 5 h. p.m. If cortisol at 5 p.m. < 410 nmol/L = impaired circadian rhythm • Free cortisol in urine 50 - 250 nmol/day Testing of thyroideal x glucocorticoid function • Thyroid function - TSH • Glucocorticoid function - ACTH ??? • Glucocorticoids and ACTH Circadian rhythm Stress, physical activity, …… Ectopic syntesis ACTH - secretion of androgens Hypercorticism (Cushingův sy.) • Types Peripheral (20 %) - suprarenal gland Central (70 %) - hypophysis Paraneoplastic (ectopic production of ACTH) • Laboratory tests Free cortisol - urine Rhythm of plasma cortisol (impaired) Serum cortisol: 8 h. and 17 h. Impaired circadian rhythm = early sign of Cushing sy ACTH Diff. dg. primary x secondary hypercorticism • Dexamethasone supression test Function of negative feedback ↓ secretion CRH, ACTH,  ↓ cortisol (< 50 %) Adenoma SR gland - without ↓ cortisol (no response) • CRH stimulating test ↑ACTH,  ↑cortisol (> 50 %) Cushing - exaggerated reaction Ectopic secretion of ACTH - no response Hypercorticism - lab. tests (functional tests) • Glycaemia Prediabetes, diabetes • Ionts Hypokalaemia, MAL Hypercorticism - other lab. tests Hypophysis (Cushing dis.) Ektopic production ACTH Tumour of the cortex suprarenal gl. ↑ ↑ ↑ ↑ ↑ Inhibition of circandian rhythm only ↑ ↑ ↑ Inhibition of circandian rhythm only ↑ ↑ ↑ ↑ ↓ ↓ without response without response without response Diff. dg. - Cushing syndrom • Primary - Addison´s disease Autoimmune, infection, …. • Secondary - due to deficit of ACTH Pituitary diseases • Lab. tests Serum cortisol Plasma ACTH Diff. dg. central x periferal form Stimulating tests Hypocortisolizmus • ACTH test (synacthen test) Synthetic ACTH  ↑ cortisol ↑ cortisol > 700 nmo/l  adrenocortical insuff. is excluded Stimulating test (suspicion of central hypocorticalism) Testing of glucocorticoid secretion • Hypocorticalism Cortisol in serum ACTH in serum Stimulation tests (Synacten - ACTH, Metyrapon) • Hypercorticalism Cortison in urine Cortisol in serum - circadian rhythm ACTH in serum Supression test (dexamethazon) Stimulation test (CRH) Lab tests - mineralocorticoids Na+, K+: serum, urine output/d., Fractional excretion PRA (plasma renin activity) Blood collection - morning in bed rest Positional changes or stress readily increase the PRA Plasma aldosterone Blood collection - morning in bed rest Captopril test Renovascular x essential hypertension Captopril = inhibitor ACE (angiotensin converting enz.) Distinct ↑of PRA = renovascular h. • Congenital adrenal hyperplasia (CAH) Adrenogenital syndromes (AGS) • Neonatal screening: 17α-OH-progesterone • ACTH test (synacthen test) Synthetic ACTH  ↑ cortisol ↑ cortisol > 700 nmo/l  adrenocortical insuff. is excluded • Insulin stimulating test Hypoglycaemia (< 2,2 mmol/L)  ↑ CRH, ACTH, cortisol Diff. dg. Cushing sy. x overproduction of corticoides due tu stress • Metyrapone blocking test Metopirone inhibits 11β-hydroxylase (cortisol synthesis) ↓ cortisol  ↑ ACTH  ↑ stimulation of SR gland  ↑ 11-deoxycortisol synthesis Measuring of serum cortisol and urine 17-OH-steroids Week response - ectopic ACTH secretion High response - Cushing´s disease Stimulating tests (suspicion of central hypocorticalism) Adrenal medulla • Adrenaline, Noradrenaline, Dopamine • Hyperfunction - pheochromocytoma Pheochromocytoma - lab. tests • Adrenaline, NA • Metabolites  Metanefrine, normetanefrine • Serum, urine • Clonidine test  Inhibition of NA releas from sympatic n. system  No inhibition NA from pheochromocytoma • Glukagone test  Glukagone i.v.  Pheochromocytoma - 3x ↑ adrenaline, NA  Risk of hypertension crisis Adrenogenital syndromes (AGS) - lab. tests • 17α-hydroxyprogesterone Deficiency of 21-hydroxylase Simple virilizing, salt-wasting form 17α-OH-progesterone: norm.- mírně ↑ Synacthen test: ↑ > 30 nmol/L za 60 min (fysiol. < 18 nmol/L). • 11-deoxycortisol Deficit 11β-hydroxylázy ↑ > 350 pmol/L (spolu s 11-desoxykortikosteronem)  ↑ ↑ po Synacthenu u homozygotů • S-DHEA-sulfát bez androgenní aktivity Skrece nadledv.(nepatrně gonádami) Sérum 800 – 7 000 nmol/L ↑ u nádorů, hyperplazie nadledvin, u hirsutismu