Case 1 involves a 50-year-old woman with symptoms of weight gain, fatigue, memory loss, slow speech, dry skin, constipation, and cold intolerance. On examination, she has a puffy face and thick skin, with a slightly enlarged thyroid gland. Laboratory tests show low T4, high TSH, and normal cholesterol, consistent with hypothyroidism. Case 2 involves another 50-year-old woman with similar symptoms plus postural dizziness and a deepened voice. Her thyroid gland is not palpable on examination. Laboratory tests again show low T4, elevated but less elevated TSH than Case 1, and high cholesterol, also consistent with hypothyroidism.

1. Dr Prasenjit Mitra
Senior Resident
AIIMS Jodhpur

2. Case 1
• History:
• A 50 year old housewife complains of progressive weight gain
of 20 pounds in 1 year, fatigue, slight memory loss, slow
speech, dry skin, constipation, and cold intolerance.
• Physical examination:
• Vital signs include a temperature 96.8oF, pulse 58/minute and
regular, BP 140/100. She is moderately obese and speaks
slowly and has a puffy face, with pale, cool, dry, and thick
skin. The thyroid gland is slightly enlarged, firm, not nodular,
mobile, and not tender. The deep tendon reflex time is
delayed.
• Laboratory studies:
• CBC and differential WBC are normal. The serum T4
concentration is 3.8 ug/dl (N=4.5-12.5), the serum TSH is 23.0
miU/ml (N=0.2-3.5), and the serum cholesterol is 255 mg/dl.

3. Case 2
• History:
• A 50 year old housewife complains of progressive weight gain
of 20 pounds in 1 year, fatigue, postural dizziness, loss of
memory, slow speech, deepening of her voice, dry skin,
constipation, and cold intolerance.
• Physical examination:
• Vital signs include a temperature 96.8oF, pulse 58/minute and
regular, BP 110/60. She is moderately obese and speaks
slowly and has a puffy face, with pale, cool, dry, and thick
skin. The thyroid gland is not palpable. The deep tendon
reflex time is delayed.
• Laboratory studies:
• CBC and differential WBC are normal. The serum T4
concentration is 3.8 ug/dl (N=4.5-12.5), the serum TSH is 1
miU/ml (N=0.2-3.5), and the serum cholesterol is 255 mg/dl
(N<200).

4. Hypothyroidism
A deficiency in thyroid hormone production or secretion producing a
variety of clinical signs and symptoms of hypometabolism.
Often overlooked  may present with serious signs and symptoms.
Treatable with a good prognosis.
Prevalence - undiagnosed hypothyroidism 5%, previously diagnosed
hypothyroidism 3%
Incidence – 226 per 100,000 per year

5. Hypothyroidism
Worldwide, the most common cause of
hypothyroidism is still iodine deficiency.
In developed countries, the most common cause of
primary hypothyroidism is Hashimoto thyroiditis.
Hypothyroidism
• is more common in women than men,
• increases with age
• higher in whites than in blacks or Hispanics

6. Classification
Age of onset
• Congenital
• Acquired
HPT level
• Primary (defect in the thyroid)
• Secondary (defect in the
hypothalamus or pituitary gland, also
called central hypothyroidism)
Severity
• Overt (clinical)
• Mild [subclinical)
Duration
• Permanent
• Transient

7. Primary Hypothyroidism
Thyroid dysgenesis
Destruction of thyroid tissue
Chronic autoimmune thyroiditis: atrophic and goitrous forms
Radiation: 131I therapy for thyrotoxicosis, external radiotherapy to
the head and neck for non-thyroid malignant disease
Subtotal and total thyroidectomy

8. Primary Hypothyroidism
Infiltrative diseases of the thyroid (amyloidosis, sarcoid, lymphoma,
hemochromatosis, scleroderma)
Defective thyroid hormone biosynthesis
Congenital defects in thyroid hormonal biosynthesis
Iodine deficiency
Drugs with antithyroid actions: lithium, iodine and iodine containing
drugs, radiographic contrast agents

9. Central hypothyroidism
Insufficient stimulation by TSH of an
otherwise normal thyroid gland.
Prevalence -
• 1 : 20,000 - 80,000
• 1 in 1000 hypothyroid patients.
• 1 in 160,000  congenital hypothyroidism of
central origin.

10. Central Hypothyroidism
• pituitary macroadenomas, craniopharyngiomas,
meningiomas, gliomas, Rathke cleft cysts,
metastases, carotid aneurysms
Invasive
lesion
• cranial surgery or irradiation, drugsIatrogenic
• head traumas, traumatic deliveryInjury
• postpartum necrosis (Sheehan syndrome),
pituitary apoplexyInfarction

11. Central Hypothyroidism
• lymphocytic hypophysitis, circulating anti-POU1F1
antibodies
Immunologic
disease
• sarcoidosis, hemochromatosis, histiocytosis XInfiltrative lesion
• tuberculosis, syphilis, mycosesInfectious disease
• pituitary transcription factor defects (occasionally
with childhood onset), TSHβ and TRHR mutationsInherited
• Other unknown causes Empty sella syndromeIdiopathic

12. Signs and Symptoms
Symptoms
• Tiredness, weakness
• Dry skin
• Feeling cold
• Hair loss
• Difficulty concentrating, poor memory
• Constipation
• Weight gain with poor appetite
• Dyspnoea
• Hoarse voice
• Menorrhagia (later oligomenorrhea or
amenorrhea)
• Paresthesia
• Impaired hearing

13. Signs and Symptoms
Signs
• Dry coarse skin; cool peripheral
extremities
• Puffy face, hands, and feet (myxedema)
• Diffuse alopecia
• Bradycardia
• Peripheral edema
• Delayed tendon reflex relaxation
• Carpal tunnel syndrome
• Serous cavity effusions

14. Laboratory Evaluation
Reference – Harrison’s Endocrinology, 4th ed.

15. Laboratory Evaluation
Reference – Williams Endocrinology, 13th ed.

16. Laboratory Evaluation
Reference – Williams Endocrinology, 13th ed.

17. Pre-analytical Variables
Age
Pregnancy
TSH/FT4 relationship
Biological differences
Age
• Both TSH and FT4
concentrations are higher in
children, especially in the 1st
week of life and throughout
the 1st year.
• TSH increases with age
• Increased Mean variability
Pregnancy
• ↑ Estrogen levels  ↑ 2-3x mean TBG
concentration than pre-pregnancy level by 20
weeks of gestation  shift in the TT4 and
TT3 reference range to approximately 1.5
times the nonpregnant level by 16 weeks of
gestation
• ↑ HCG levels cross-react partly with TSH
receptor  mildly suppressed levels.
• The peak rise in HCG and nadir in serum TSH
level occurs together at about 10-12 weeks of
gestation.

18. Analytical methods
Gold Standard - Equilibrium dialysis.
• Complex and not widely available.
Commonly used methods - one-step or
two-step immunoassay method.
• Two-step method more reliable than one-step
method.
Chemiluminescence

19. Analytical methods
Analytical interferants - Heterophile
antibodies
• Falsely high or low TFTs.
• Antibodies induced by external antigens
(heterophile antigens) that cross-react with self-
antigens.
• Human anti-mouse antibodies (HAMA)  Reacts
with the mouse monoclonal antibodies (used in
many immunometric assays like TSH estimation)
 erroneously high or low TSH values

20. Analytical methods
Analytical interferants - Macro-TSH
• Rare condition
• Serum contains antibodies against TSH (anti-TSH
Ig)  binds to TSH and neutralizes its activity, but
leaves open epitope to interact with assay
antibodies leading to spuriously high value.
• Detected by:
• Linearity test
• PEG precipitation
• TSH sequestration test
• Gel filtration chromatography

21. Analytical methods
Specimen
• Serum is preferred specimen and ideally whole
blood samples should be allowed to clot for more
than 30 min and then centrifuged and separated.
Storage
• 4-8°C for up to 7 days or −20°C (Long-term).
Collection
• Barrier gel tubes does not affect the results of
TFTs.

22. Analytical methods
Stability
• Quite stable.
• TSH and T4 in dried whole blood spots used to
screen for neonatal hypothyroidism are also
stable for months when stored with a desiccant.
Interferants
• Hemolysis, hyperlipidemia, and
hyperbilirubinemia do not produce interference
in hormone estimation by different assays

23. Measurement of TSH
Immunometric assays with chemiluminescent probes and
solid phase capture Antibodies  analytical sensitivity.
Sensitivity is a major issue  it is necessary to measure
well below the population reference interval to
differentiate primary hyperthyroidism from other causes
of low serum TSH concentration.
The previously used “generational” concept for TSH
assays is now largely redundant because clinical
guidelines now specify the appropriate sensitivity
required for TSH assays.

24. Measurement of TSH
First-generation assays  sensitive enough only to
discriminate normal from hypothyroid subjects
Second-generation assays  detect TSH below the
reference interval but not well enough to reliably
discriminate primary hyperthyroidism from other causes
of low TSH.
All assays in clinical practice should be “third generation,”
that is, they should have a coefficient of variation (CV) of
less than 20% (functional sensitivity) at a concentration
of 0.01 mIU/L.

25. Measurement of T3 and T4
Assay Hierarchy
Direct
Equilibrium dialysis
Ultrafiltration
Indirect
Immunoassay
One step
Immunoassay
Two step
Immunoassay
Free Hormone hypothesis

26. Measurement of T3 and T4
fT4
pbT4
Dialysis/Ultrafiltration
Competitive
immunoassay
Mass
Spectrometry

27. Measurement of T3 and T4
Indirect immunoassay methods
• make the assumption that the fT4:tT4 equilibrium is
maintained during immunoassay to an extent sufficient to
return a clinically relevant estimation of fT4.
One-step methods
• incubate the assay antibody and tracer in the presence of all
serum constituents.
Two-step or “back-titration” methods
• allow T4 to equilibrate with the assay antibody in the presence
of all serum components but wash away uncaptured
components before back titrating with tracer.

28. Measurement of T3 and T4
Estimation of total T3 and T4
• Mass spectrometric measurements are now
the method of choice  straightforward with
high sensitivity and selectivity.
• Competitive immunoassay
• These methods include a displacing agent
such as 8-anilino-1-napthalene-sulfonic acid to
release thyroid hormone from high-affinity
serum binding sites

29. Reference ranges

30. Further investigations
Calcitonin
Thyroglobulin
Immunological test
• TPOAb, Anti-TRAb, Anti- TgAb

31. Inference
• Hypothyroidism is the commonest disorder of thyroid function.
• It is more common in women, and the risk of developing
hypothyroidism increases with age.
• Hypothyroidism is a known risk factor for cardiovascular disease.
• Excluding the newborn period and iodine deficiency, AITD is the
most common cause of primary hypothyroidism.
• Central hypothyroidism (TSH deficiency) is a rare cause of
hypothyroidism.

32. Recent advances
Allen Herndon Dudley syndrome
• Mutation in monocarboxylate transporter-8 gene  required
for thyroid hormone transportation into various cells  raised
T3, low T4, and normal or elevated TSH
Thyroid receptor-α mutation
• A similar hormonal profile with raised T3, low T4, and normal
TSH  Thyroid resistance
Iodotyrosine deiodinase deficiency
• Genetic condition
• have raised T4, normal/low T3, and normal TSH levels.
• Serum and urinary measurement of monoiodothyronine and
diiodothyronine is used to detect

33. Recent advances
Reference – Harrison’s Endocrinology, 4th ed.

34. Case 1
• History:
• A 50 year old housewife complains of progressive weight gain
of 20 pounds in 1 year, fatigue, slight memory loss, slow
speech, dry skin, constipation, and cold intolerance.
• Physical examination:
• Vital signs include a temperature 96.8oF, pulse 58/minute and
regular, BP 140/100. She is moderately obese and speaks
slowly and has a puffy face, with pale, cool, dry, and thick
skin. The thyroid gland is slightly enlarged, firm, not nodular,
mobile, and not tender. The deep tendon reflex time is
delayed.
• Laboratory studies:
• CBC and differential WBC are normal. The serum T4
concentration is 3.8 ug/dl (N=4.5-12.5), the serum TSH is 23.0
miU/ml (N=0.2-3.5), and the serum cholesterol is 255 mg/dl.

35. Case 2
• History:
• A 50 year old housewife complains of progressive weight gain
of 20 pounds in 1 year, fatigue, postural dizziness, loss of
memory, slow speech, deepening of her voice, dry skin,
constipation, and cold intolerance.
• Physical examination:
• Vital signs include a temperature 96.8oF, pulse 58/minute and
regular, BP 110/60. She is moderately obese and speaks
slowly and has a puffy face, with pale, cool, dry, and thick
skin. The thyroid gland is not palpable. The deep tendon
reflex time is delayed.
• Laboratory studies:
• CBC and differential WBC are normal. The serum T4
concentration is 3.8 ug/dl (N=4.5-12.5), the serum TSH is 1
miU/ml (N=0.2-3.5), and the serum cholesterol is 255 mg/dl
(N<200).

36. Thank you …