Clinical Biochemistry and Metabolic disease II

Dr Vivion Crowley

Consultant Chemical PathologistSt James’s HospitalDublin

Biochemical Investigation of a Patient with Suspected Hypocalcaemia?

What are the causes of HypocalcaemiaLow albumin

Artefact

Chronic renal failure

Hypoparathyroidism

PTH resistance-Pseudohypoparathyroidism-Hypomagneaemia

Vitamin D deficiency

Vitamin D resistance states

Medications

Miscellaneous-Pacreatitis-Sepsis-Tumour lysis syndrome

What are the clinical features of Hypocalcaemia

•PNS: numbness, tingling, muscle cramps

•CNS: Psychiatric symptoms e.g irritability, rarely tetany and seizures

•Basal ganglia calcification

•Chvostek’s sign

•Trousseau’s sign

Does the patient have “True HypoCa”

What is the corrected Ca?

Evidence of artefact? - K EDTA contamination

What is the local reference range?

What is the Plasma PO4 level?High PO4

•Hypoparathyroidism•Renal failure

Low/Normal PO4

•Vitamin D•Renal failure – post dialysis/treatment•Other causes

NB: PO4 levels are affected by many factors and cannot be relied upon alone

Does the patient have Hypomagnesaemia?

-Causes PTH resistance-Must correct Mg deficit before improvement in Ca levels

Is there a clinically apparent cause of Hypocalcaemia?

Chronic Renal Failure – high PO4, low 1, 25 (OH) Vit D

Pancreatitis – precipitation of Ca and Mg in necrotic adipose tissue

Sepsis – low albumin

Post thyroid or parathyroid surgery – “Hungry bone syndrome”

Tumour lysis syndrome – high PO4 precipitates Ca

Rhabdomyolysis – as for TLS, marked increase in CK

Osteoblastic metastases

What about Calcium-reducing medications

Bisphosphonates

Calcitonin

Phosphate

Foscarnet

Pentamidine

What is the plasma PTH Level?

Low PTH

•Hypoparathyroidism

-Idiopathic – Di George syndrome-Autoimmune-Post-surgical-Hypomagnesaemia

High PTH

•Vitamin D deficiency or resistance (secondary Hyperparathyroidism)•Psuedohypoparathyroidism•Severe liver disease•Chronic renal failure

NB: Check Vit D levels in secondary hyperparathyroidism

43 yr old male with renal failure due to analgeisc nephropathy

Na 134K 5.8Urea 42.2Creat 650Ca 1.82PO4 2.53Alb 37ALP 200PTH 425

What is the cause of his HypoCa?

Explain the abnormal findings?

70 yr old male presented with the Hx of Bone pain and malaise

Ca 3.4PO4 1.5Alb 30TP 110ALP 100

What is the corrected Ca level?

What further investigations would you consider?

The PTH is 10 (9-65), is the HyperCa PTH dependent or independent?

What is the likely diagnosis?

What is MGUS?

Case 2

• GM 73 old female• Admitted April and July 2008 with

– Left sided weakness, slurred speech, confusion– Mild seizures on 2nd admission– Poor oral intake, weight loss (57.5 kg on 1/5/08 –48.5 kg

on 22/07/08)

• PMH: HTN, Hypercholesterolaemia, OA• Medication: Aspirin, Doxazocin, Perindopril Amlodipine, Omeprazole Pravastatin

Case 2 cont.

• Routine bloods:– GluR 5.5 mmol/L

– U/Es: urea 20.9…5.4 mmol/L, creatinine 202…66 umol/L (after rehydration), Na 140 mmol/L, K 2.9 mmol/L

– Ca 1.24 mmol/L Albumin 28 g/L, PO4 1.16 mmol/L (ref. 0.8-1.4)

– LFTs NAD

Case 2 cont.

• Laboratory tests cont.

– FBC- Hb 10.3, MCV 77.7, tTG 1.6, iron 2 (ref 14-3) umol/L, transferin sat. 7 (ref 30-40) %, ferritin and folate NAD

– TFTs TSH 0.71 mU/L, fT4 23 pmol/L

– 25OH Vit D 32 nmol/L (>80)

– PTH 148.5 pg/mL (ref 15-65)

Case 2 cont

• Mg 0.15( 0.7-1.0) mmol/L,

Case 2 cont.

• Other investigations:

– CXR/PFA NAD– OGD/Colonoscopy NAD– AUS: loss of normal cortical medullary

differentiation– MRI brain NAD

Case 2 cont.

• Treatment: – iv Magnesium 7 g in total

– Vit D2 50 000 iu im

– Magnesium Verla 5 g bd ( 5g equiiv. 5 mmol or 121.5 mg magnesium)

– One-Alpha 0.5 mcg (alfacalcidol) for 1/52

– Calcichew D3Forte ii od (one tablet= 400 IU Vit D3, 500 mg Ca++carbonate)

– Kay-Cee-L (75 mg KCl per 1 mL)

25/4 22/7 28/8 13/11

Ca 1.24 1.72 2.44 2.46

Mg 0.15 0.11 0.89 0.89

K 2.9 2.5 4.4 4.6

25 OH

VitaminD

32 35 41 79

Albumin 28 32 40 42

PTH 148 19

Biochemical test play an essential role in the management of endocrine disease

Screening – TSH in neonatal hypothyrroidism

Case finding – e.g. Pentagastrin test in medullary thyroid ca

Diagnosis – over or under production of hormones

Monitoring response to Rx or recurrence

Disorders of Endocrine Glands

Underactivity with under production of normal hormone

Overactivity with over production of normal hormone

Inappropriate production of hormone not normally produced

Ectopic production of hormone by a non-endocrine gland

Disorders involving the Pituitary Gland

Hypopituitarism

Partial or complete deficiency of anterior and/or posteriorpituitary hormones

Causes

•Pituitary tumours•Parapituitary tumours e.g. craniopharingioma, metasases•Radiotherapy•Apoplexy (infarction)•Infiltration – sarcoidosis, histiocytosis x, haemochromatosis•Infections – TB, abscess•Trauma- post head injury•Genetic syndromes e.g. Kallmann’s syndrome, Laron dwarfism

GH Children – growth delay

Adults – GHD

FSH/LH Delayed puberty

Oligo/amenorrhoea

Erecile dysfunction + testicular atrophy

Loss of secondary sex characteristics

ACTH hypoadrenalism

TSH hypothyroidism

Prolactin Failure of lactation

AVP (ADH) Diabetes insipidus

Hypopituitarism- Clinical Manifestations

Hypopituitarism – Biochemical investigation

Basal hormone levels

-LH, FSH, Testo / E2-TSH and T4-9am cortisol-Prolactin (PRL)-IGF-1 (marker of GH action)

Dynamic function tests

-Insulin tolerance test (ITT) – for Cortisol and GH response-GnRH test for LH, FSH reserve-TRH test for TSH reserve (rarely used now)

Also need to consider imaging pituitary gland – MRI, CT

Acromegaly - Excess GH secretion

CausesPituitary tumour-Macroadeneoma >10mm-Microadenoma <10mm

Clinical presentaionPituitary gigantism in childhood

Acromegalic symptoms-Increased sweating-Headaches-Fatigue/tiredness, joint pains-Change in shoe size, ring size

Acromegaly – clinical signs

•Facial appearances - characteristic•Deep voice•Macroglossia•Enalarged hands/feet•Carpal tunnel syndrome

Biochemical Investigation of Suspected GH Excess

Oral glucose tolerance test (75g load)-in acromegaly there is a failure to suppress GH to < 2 mU/L

IGF-1 – usually elevated

Check other pituitary hormones ( see in Hypopit section)

Imaging of pituitary

Cushings’ syndrome - Excess circulating cortisol

Causes1. Exogenous steroids2. ACTH secreting pituitary tumour3. Ectopic production of ACTH4. Adrenal tumour

Clinical Features- Facial appearance – moon facies, plethoric complexion, acne- Weigt gain – central obesity, “buffalo hump”- Thin skin, easy bruising, - Proximal muscle weakness- Mood disturbance- Menstrual disturbance, hirsutism- Hypertension

Cushing’s Syndrome

Investigation of suspected Cushing’s syndrome

Does the patient have Cushing’ syndrome?

What is causing the patient’s Cushing’ syndrome?

Does the Patient have Cushing’s syndrome?

Out-patient tests

Overnight dexamethasone suppression (1mg at midnight)Normal = 9am cortisol < 50nmol/l

24 hour urinary free cortisol

In-patient tests

Midnight cortisol – looking for loss of cicardian rhythm

Low dose dexamethasone suppression test (0.5mg qds for 48hour)Normal = 48hr cortsiol < 50 nmol/l

What is the underlying cause of Cushing’s syndrome?

Plasma ACTH levelACTH-dependent if non-suppressed or elevated- Pituitary- Ectopic

ACTH independent if suppressed-Adrenal

To differentiate Pitutary ad ectopic causesHigh dose dexamethasosne suppression (2mg qds x 48hr)-Pituitary suppresses to < 50% basal value

CRH test-exagerated cortisol and ACTH response in pituiray Cushing’s

Inferior petrosal sinus sampling + pituitary imaging

Hyperprolactinaemia

Condition Example

Physiological Pregnacy, lactation

Idiopathic

Stress venepuncture

Drugs Dopamine agonistse.g

Phenothiazines

Chronic liver/renal disease Cirrhosis, CRF

Hypothalamic/pituitary

disorders

Micro/macroadneoma

Stalk compression syndrome

Primary hypothyroidism

PCOS

Hyperprolactinaemia – clinical presentation

Females

-Oligo/amenorrhoea-Galatorrhoea-Infertility-Reduced libido-Symptoms relating to pituitary tumour

Males

-Symptoms relating to pituitary tumour e.g. headache, visual disturbance#-Less frequently, reduced libido, infertility, galatorrhoea

Biochemical investigation of Hyperprolactinaemia

Plasma Prolactin-At least two confirmed elvations in plasma prolactin-Must screen for Macroprolactinaemia ( a high mol wt form of circulating prolactin)-Macroprolactinaemia is not clinicall significant-Prolactin levels > 5000mU/L are indicative of a pituitary adenoma

Check routine bloods-renal and liver function-TFTs-Pregnancy test (hCG)-FSH/LH, E2

Imaging of pituitary gland if indicated

What are the commonly measured TFTs?

Total T4 – includes protein bound and Free Thyroxine-Free Thyroxine is the active hormone-TBG is the main protein binding Thyrxoine-Increased TBG s seen in pregnancy

Free T4 (FT4)

TSH – reflects the pituitary response to FT4 level

Total T3 – useful in the diagnosis of T3 toxicosis- Normal T4 and suppressed TSH

Patterns of Thyroid Function Tests

Hypoglycaemia

Definition: plasma glucose < 2.8mmol/l (blood glucose < 2.2mmol/l)

Clinically presents with - adrenergic features, neuroglycopaenia

“Whipple’s triad” -

•Symptoms & signs of hypoglycaemia•Plasma glucose < 2.8mmol/l•Relief of symptoms by glucose intake (infusion/oral)

Hypoglycaemia

Causes:Drug therapy - Insulin, Sulphonylurea, -blockers, QuinineFactitious - Insulin, sulphonylureas (healthcare workers)

Fasting Hypoglycaemia

InsulinomaHepatic failure - gluconeogenesisSepsis, Cardiac failureHypopituitarism, Addison’s disease

Tumour-related hypoglycaemia - mesenchymal tumours e.g. fibrosarcoma etc.? Ectopic IGF II by tumour cells

Autoantibodies - Insulin, Insulin receptor

HypoglycaemiaReactive HypoglycaemiaIdipopathicEarly diabetesPost-gastric surgery

Investigations:

Ensure that hypoglycaemia is documanted by laboratory blood/plasma glucoseDetermination on a sample collected into a fluoride tube

5hour OGTT - hypoglycaemia may occur between 2-5 hours after glucose load

Definitive investigation for fasting Hypoglycaemia:Supervised - 72 hour prolonged fastIf pt develops neuroglycopaenic symptoms then measurePlasma Glucose, Insulin, C-pepetide

Other routine invsetigations: U/E, LFTs, ? Endocrine

Polyuria

Urine output > 3 litres/day(explain the difference between polyuria and urinary frequency)

Confirm polyuria - 24hr urine collection

Causes of polyuria

Drugs - diuretics, lithiumDiabetes mellitus - fasting ± random glucose, OGTTChronic renal failure - plasma urea & creatinine, Creatinine clearance

Hypokalaemia

Hypercalcaemia

Polyuria

In clinical practice the most common reason for doing a water deprivation test is to differetiate between

• Psychogenic polydipsia

• Diabetes Insipidus - central AVP (ADH) deficiency - nephrogenic AVP action on renal tubule

Water Deprivation test ± vasopressin administration

Addison’s Disease

Primary adrenal insufficiency - differentiate from secondary i.e. ACTH deficiency - tertiary :CRH suppression by exogenous steroids

Clinically Weakness, fatigue, anorexia, wt loss, postural hypotension, Coma

Hyperpigmentation - elbows, knees, buccal mucosa, recent scars (ACTH levels)

Causes

•Autoimmune - ? Polyglandular autoimune syndromes•Infections - TB, fungal infections, HIV•Metastatic disease - lung, Breast, colon (bilateral disease)•Medications - ketoconazole

•Waterhouse Freidrickson - bilateral adreanl haemorrahage (sepsis e.g menigococcus)

Biochemical abnormalities in Addison’s Disease

•Hyponatraemia•Hyperkalaemia•Pre-renal failure plasma urea & creatinine•? Hypercalcaemia•Abnormal TFTs - TSH, T4 (hypothyroid picture)- May be a transient pictureNB: treat hypoadrenalism before giving L-T4

Acute presentation:

Take blood sample for plasma Cortisol and ACTH levels before steroid administration

Plasma Cortisol Plasma ACTH

NB: Dexamethasone does not interfere with cortisol assay

Biochemical Diagnosis of Addison’s disease

Chronic Presentation

Short synacthen test -does not differentiate between primary and secondary-Synacthen 250 μg IM-0, 30 and 60 min plasma cortisol-30 min Plamsa Cortisol > 550 nmol/L

Long synacthen test

Adrenal antibodies

Biochemical paraneoplastic syndromes

Tumours of specific endocine glands e.g. insulinoma, pituitary etc.

Hypercalcaemia of malignancy

Syndrome of inappropriate antidiuresis (SIAD) - hyponatraemia

Cushing’s syndrome

Tumour-induced hypoglycamia

Tumour-induced osteomalacia - mesenchymal tumours (hemangiopericytoma) Normal Ca, PO4, 1,25 (OH)2 Vit D ??Renal phosphate wasting

Carcinoid syndrome - facial flushing, diarrhoea, brochospasm

Laboratory diagnosis - urinary 5 hydroxyindole actetic acid (5HIAA)

Case 1: Hx

35 yr old male

Hx EBV infection 8 weeks previously

No medical or family hx of note otherwise

Not on regular medication

C/O vague/nonspecific symtoms, fatigue

GP performed “routine blood tests” including TFTs

Case 1: TFTs

TT4= 223 (63-142)

TSH= 4.87

Repeated 2-3 weeks later

TT4 = 171

TSH = 2.89

Case 1: TFTs (cont)

FT4 = 51.3 (9-24)

T3 = 3.5 (0.8-2.5)

Biochemical Hyperthyroidism

No clinical features of thyrotoxicosis

No biochemical evidence of heterophile ab interference

No family hx of thyroid dx

Case 1: Differential Dx

TSHoma

Thyroid hormone resistance (RTH) - Refetoff’s syndrome

FDH – rare

Heterophile abs

MRI scan of pituitary – Macroadenoma - TSHoma

Case 2: HistoryPhone call from a GP regarding TFTs:

54 yr old male – vague hx fatigue

T4 = 40 (69-141)

TSH = 1.53

Sample recovered and tested for

FT4 = 5.7 (9-24)

TBG = 25 (13-24)

A large clot was noted in serum

R/O artefact – repeat investigation with

Case 2: Repeat TFTs

•TT4 = 44•FT4 = 4.9•TSH= 1.2•Cortisol = 130 (random am)•Testo = 10.5 (8.7 –33.0)•LH = 2.4•FSH = 6.3•GH < 1.0•IGF-1 < 25•PRL = 419 (70-413)

Central Hypothyroidism – Referred to endocrine service SJH

Case 2: Endocrine assessment

Stimulation testing (ITT)

-Achieved hypoglcaemia

-GH deficient

-ACTH/Cortisol deficient

-Centrally hypothyroid

MRI scan – empty sella ? cause

Case 3: Background

23 yr old male

Hx Migraine and fatigue

GP performed TFTs

TT4 = 43

TSH = 2.89

Biochem Registrar signing out - ? Hypothyroid - Put on some additional test

FT4 = 5.8 (9-24)

Case 3: Endocrine tests

More additional tests after discussion with GP

•Cortisol = 97 (244-727) but NB diurnal variation

•FSH = 2.7 (1.0-10.5)

•LH = 2.2 (1.0 –6.0)

•Testo = 1.3 (8.7-33)

•Prolactin = 4490 (70-413)

•Post fractionation Prolactin (PFP) = 3960

Case 3: Diagnosis

Biochemical Dx:

-Hypothyoid-Hypogonadal-Hypocortisolaemic-Hyperprolactinaemic

Hypopituitarism

MRI scan – Macroadenoma - ? Macroprolactinoma

Case 4: background

43 yr old female

Hx Spina Bifida (wheel chair bound)

Currently in Cheshire Home

4/52+ hx malaise

Admitted to St Elsewhere

Atonic Bladder

Renal impairement

GP to monitor U/Es

Case 4:

5/5 6/5 12/5

Na 165 162

K 3.6 3.0

Urea 14.2 6.9

Crea 167 133

POsmo 352

UOsmo 410 222

Gluc 13.6 9.7** fasting

•Result brought to attention of Consultnat Chem Path•Hypernatraemia ? Cause

Case 4: Dx?

Results suggestive of

-DI-DM

Paired urine and plasma osmolality are very usefulin directing management of

-hypernatraemia-hyponatraemia

24 yr old male

Unwell – Hx of admissions with hypoNa

Na 121K 5.5Urea 9.3Crea 118

T4 83TSH 4.97

Cortisol 52ACTH 1122