hashimoto's thyroiditis

1. Hypothyroidism
Hashimoto’s Thyroiditis
DR LAXMI RAJ BHATTA
RESIDENT
INTERNAL MEDICINE

2. INTRODUCTION
• The thyroid gland produces two related hormones - thyroxine (T4) and
triiodothyronine (T3) .
• Acting through thyroid hormone receptors α and β,
• Cell differentiation, organogenesis, maintain thermogenic and metabolic
homeostasis
• TSH is measured using IRMA (immunoradiometric) assays that are highly
sensitive and specific as well with CLIA ( chemiluminescent immunoassay )

4. • The thyroid gland consists of
• numerous spherical follicles composed of thyroid follicular cells that surround
secreted colloid (a proteinaceous fluid containing large amounts of
thyroglobulin, the protein precursor of thyroid hormones).
• TSH binds to its receptor on the basolateral surface of the follicular
cells.
• This binding leads to Tg reabsorption from the follicular lumen and
proteolysis within the cytoplasm, yielding thyroid hormones for
secretion into the bloodstream.

7. THYROID FUNCTION IN PREGNANCY
• Five factors alter thyroid function in pregnancy:
• Transient increase in hCG during the first trimester - weakly stimulates the
TSH-R;
• the estrogen-induced rise in TBG during the first trimester – also sustained
during pregnancy;
• alterations in the immune system, leading to the onset, exacerbation, or
amelioration of an underlying autoimmune thyroid disease;
• increased thyroid hormone metabolism by the placenta; and
• increased urinary iodide excretion, which can cause impaired thyroid
hormone production in areas of marginal iodine sufficiency.

8. • The rise in circulating hCG levels during the first trimester is
accompanied by a reciprocal fall in TSH that persists into the middle
of pregnancy.
• The RDA is 220 μg iodine per day for pregnant women and 290 μg
iodine per day for breastfeeding women.
• American Thyroid Association has recommended that all pregnant and
breastfeeding women in the United States and Canada take a prenatal
multivitamin containing 150 μg iodine per day. Urinary iodine is >10 μg/dL in
iodine-sufficient populations.

9. • Normative values for most thyroid function tests differ during pregnancy
• if available, trimester specific reference ranges should be used when diagnosing thyroid
dysfunction during pregnancy.
• TSH levels decrease during the first trimester and then rise as gestation
progresses.
• Total T4 and T3 levels are about 1.5× higher throughout pregnancy but the free
T4 progressively decreases so that third trimester values in healthy pregnancies
are often below the nonpregnant lower reference cutoff.
• During pregnancy, subclinical hypothyroidism occurs in 2% of women, but overt
hypothyroidism is present in only 1 in 500.

10. • Targeted TSH testing for hypothyroidism is recommended for women
planning a pregnancy
• if they have a strong family history of autoimmune thyroid disease, other
autoimmune disorders (e.g., type 1 diabetes), infertility, prior preterm
delivery or recurrent miscarriage, signs or symptoms of thyroid disease, or are
older than 30 years.
• Thyroid hormone requirements are increased by up to 45% during
pregnancy in levothyroxine-treated hypothyroid women.

11. THYROID HORMONE TRANSPORT
• Both hormones are bound to plasma proteins, including thyroxine-
binding globulin (TBG), transthyretin (TTR, formerly known as
thyroxine-binding prealbumin, or TBPA), and albumin.

12. • The finding of an abnormal TSH level must be followed by
measurements of circulating thyroid hormone levels to confirm the
diagnosis of hyperthyroidism (suppressed TSH) or hypothyroidism
(elevated TSH).

13. Tests to Determine the Etiology of Thyroid
Dysfunction
• Autoimmune thyroid disease is detected most easily by measuring
circulating antibodies against TPO and Tg.
• About 5–15% of euthyroid women and up to 2% of euthyroid men
have thyroid antibodies;
• such individuals are at increased risk of developing thyroid dysfunction.
• Almost all patients with autoimmune hypothyroidism, and up to
80% of those with Graves’ disease, have TPO antibodies, usually at
high levels.

14. • TSIs are antibodies that stimulate the TSH-R in Graves’ disease.
• They are most commonly measured by commercially available tracer
displacement assays called TRAb (TSH receptor antibody)

15. • Serum Tg levels are increased in all types of thyrotoxicosis
• except thyrotoxicosis factitia caused by self-administration of thyroid
hormone.
• The main role for Tg measurement, however, is in the follow-up of
thyroid cancer patients.
• After total thyroidectomy and radioablation, Tg levels should be
undetectable; in the absence of anti-Tg antibodies, measurable levels
indicate incomplete ablation or recurrent cancer.

16. Radioiodine Uptake and Thyroid Scanning
• The thyroid gland selectively transports radioisotopes of iodine (123I,
125I, 131I) and 99mTc pertechnetate, allowing thyroid imaging and
quantitation of radioactive tracer fractional uptake.

17. Thyroid Ultrasound
• Valuable for the diagnosis and evaluation of patients with nodular thyroid disease.
• Evidence-based guidelines recommend thyroid ultrasonography for all patients
suspected of having thyroid nodules by either physical examination or another imaging
study.
• Using 10- to 12-MHz linear transducers, resolution and image quality are excellent,
allowing the characterization of nodules and cysts >3 mm.
• Sonographic patterns that combine suspicious sonographic features are highly suggestive
of malignancy (e.g., hypoechoic solid nodules with infiltrative borders and
microcalcifications, >90% cancer risk), whereas other patterns correlate with a lower
likelihood of cancer (isoechoic solid nodules, 5–10% cancer risk).

18. HYPOTHYROIDISM
• Iodine deficiency remains a common cause of hypothyroidism
worldwide.
• Iodine sufficiency
• Autoimmune disease (Hashimoto’s thyroiditis) and
• Iatrogenic causes (treatment of hyperthyroidism) are most common.

20. AUTOIMMUNE HYPOTHYROIDISM
Classification
• Autoimmune hypothyroidism may be associated
• a goiter (Hashimoto’s, or goitrous thyroiditis) or,
• at the later stages of the disease, minimal residual thyroid tissue (atrophic thyroiditis).
• Because the autoimmune process gradually reduces thyroid function,
• there is a phase of compensation when normal thyroid hormone levels are maintained by a rise in
TSH.
• Although some patients may have minor symptoms, this state is called subclinical
hypothyroidism.
• Later, unbound T4 levels fall and TSH levels rise further;
• Clinical hypothyroidism or overt hypothyroidism symptoms become more readily apparent at this
stage (usually TSH >10 mIU/L).

21. Prevalence
• Mean annual incidence rate of autoimmune hypothyroidism
• 4 per 1000 women and 1 per 1000 men.
• It is more common in certain populations,
• such as the Japanese, probably because of genetic factors and chronic exposure to a high-iodine diet.
• Mean age diagnosis - 60 years, and
• prevalence of overt hypothyroidism increases with age.
• Subclinical hypothyroidism
• 6–8% - women (10% over the age of 60) and
• 3% of men.
• The annual risk of developing clinical hypothyroidism about 4%
• when subclinical hypothyroidism is associated with positive thyroid peroxidase (TPO) antibodies.

23. Pathogenesis
• In Hashimoto’s thyroiditis,
• there is a marked lymphocytic infiltration of the thyroid with germinal center
formation,
• atrophy of the thyroid follicles
• In atrophic thyroiditis,
• the fibrosis is much more extensive,
• usually represents the end stage of Hashimoto’s thyroiditis
• Susceptibility to autoimmune hypothyroidism is determined by
• a combination of genetic and environmental factors,

24. • Female preponderance of thyroid autoimmunity
• most likely due to sex steroid effects on the immune response,
• A high iodine or low selenium intake and decreased exposure to
microorganisms in childhood increase the risk of autoimmune
hypothyroidism.
• Smoking cessation transiently increases incidence whereas alcohol intake
seems protective.

25. Clinical Manifestations
• Patients with Hashimoto’s thyroiditis may present because of goiter
rather than symptoms of hypothyroidism.
• usually irregular and firm in consistency.

26. • Skin –
• dry,
• decreased sweating,
• thinning of the epidermis, and
• hyperkeratosis of the stratum corneum.
• Increased dermal glycosaminoglycan content traps water, giving rise to skin
thickening without pitting (myxedema).
• Typical features include a puffy face with edematous eyelids and nonpitting
pretibial edema.

28. • Pallor,
• often with a yellow tinge to the skin due to carotene accumulation.
• Nail
• growth is retarded, and
• Hair
• dry, brittle, difficult to manage, and falls out easily.
• In addition to diffuse alopecia, there is thinning of the outer third of the eyebrows,

29. • Other common features include
• constipation and weight gain (despite a poor appetite).
• In contrast to popular perception, the weight gain is usually modest and due mainly
to fluid retention in the myxedematous tissues.
• Libido
• decreased in both sexes, and
• there may be oligomenorrhea or amenorrhea in long-standing disease, but
menorrhagia may occur at an early stage.
• Fertility is reduced, and the incidence of miscarriage is increased.
• Prolactin levels are often modestly increased and may contribute to
alterations in libido and fertility and cause galactorrhea.

30. • Myocardial contractility and pulse rate are reduced,
• leading to a reduced stroke volume and bradycardia.
• Increased peripheral resistance may be accompanied by
hypertension, particularly diastolic.
• Blood flow is diverted from the skin, producing cool extremities.

31. • Pericardial effusions (30%) but rarely compromise cardiac function
rarely cardiomyopathy.
• Fluid may also accumulate in other serous cavities and in the middle
ear, giving rise to conductive deafness.
• Pulmonary function is generally normal,
• but dyspnea may be caused by pleural effusion, impaired respiratory muscle
function, diminished ventilatory drive, or sleep apnea.

32. • Carpal tunnel and other entrapment syndromes are common, as is
impairment of muscle function with stiffness, cramps, and pain.
• On examination, there may be slow relaxation of tendon reflexes and
pseudomyotonia.
• Memory and concentration are impaired.

33. • Rare neurologic problems include reversible cerebellar ataxia,
dementia, psychosis, and myxedema coma.
• Hashimoto’s encephalopathy has been defined as a steroid-
responsive syndrome associated with TPO antibodies, myoclonus,
and slow-wave activity on electroencephalography,
• The hoarse voice and occasionally clumsy speech of hypothyroidism
reflect fluid accumulation in the vocal cords and tongue.

34. • Autoimmune hypothyroidism may be associated with signs or symptoms
of other autoimmune diseases,
• particularly vitiligo, pernicious anemia, Addison’s disease, alopecia areata, and type 1
diabetes mellitus.
• Less common associations include
• celiac disease, dermatitis herpetiformis, chronic active hepatitis, rheumatoid arthritis,
systemic lupus erythematosus (SLE), myasthenia gravis, and Sjögren’s syndrome.
• Thyroid-associated ophthalmopathy usually occurs in Graves’ disease, but
in about 5% of patients it is associated with autoimmune hypothyroidism.
• Autoimmune hypothyroidism is uncommon in children and usually presents
with slow growth and delayed facial and dental maturation.

35. • The pituitary may be enlarged due to thyrotroph hyperplasia.
• Myopathy,
• with muscle swelling, is more common in children than in adults.
• In most cases, puberty is delayed, but precocious puberty sometimes
occurs.
• There may be intellectual impairment if the onset is before 3 years and
the hormone deficiency is severe.

36. Laboratory Evaluation.
• A normal TSH level excludes primary (but not secondary) hypothyroidism.
• If the TSH is elevated, an unbound T4 level is needed to confirm the
presence of clinical hypothyroidism,

37. • Once clinical or subclinical hypothyroidism is confirmed, the etiology is
usually easily established by demonstrating the presence of TPO and Tg
antibodies >95% autoimmune hypothyroidism.
• Other abnormal laboratory findings in hypothyroidism may include
• increased creatine phosphokinase,
• elevated cholesterol and triglycerides, and
• anemia (usually normocytic or macrocytic).

38. • An asymmetric goiter in Hashimoto’s thyroiditis may be confused
• with a multinodular goiter (MNG) or thyroid carcinoma, in which thyroid
antibodies may also be present.
• Ultrasound
• used to show the presence of a solitary lesion or an MNG rather than the
heterogeneous thyroid enlargement typical of Hashimoto’s thyroiditis.
• FNA biopsy - focal nodules.

40. TREATMENT
CLINICAL HYPOTHYROIDISM
• If there is no residual thyroid function,
• Daily replacement dose of levothyroxine is usually 1.6 μg/kg body weight (typically
100–150 μg),
• ideally taken at least 30 min before breakfast.
• In many patients, lower doses suffice until residual thyroid tissue is destroyed.
• In patients who develop hypothyroidism after the treatment of Graves’
disease,
• there is often underlying autonomous function, necessitating lower replacement
doses (typically 75–125 μg/d).
• Adult patients under 60 years old without evidence of heart disease
• started on 50–100 μg levothyroxine (T4) daily.

41. • Dose adjusted on the basis of TSH levels,
• The goal of treatment - a normal TSH,
• ideally in the lower half of the reference range.
• TSH responses are gradual and
• should be measured about 2 months after instituting treatment or after any
subsequent change in levothyroxine dosage.
• The clinical effects of levothyroxine replacement are slow to appear.
• Patients may not experience full relief from symptoms until 3–6 months after
normal TSH levels are restored.

42. • Adjustment of levothyroxine dosage is made in 12.5- or 25-μg
increments if the TSH is high;
• decrements of the same magnitude should be made if the TSH is suppressed.
• Patients with a suppressed TSH of any cause, including T4
overtreatment, have an increased risk of atrial fibrillation and
reduced bone density.

43. • Once full replacement is achieved and TSH levels are stable
• follow-up measurement of TSH is recommended at annual intervals.
• It is important to ensure ongoing adherence as patients do not feel any
symptomatic difference after missing a few doses of levothyroxine, and this
sometimes leads to self-discontinuation.

44. • Such patients often have normal or high unbound T4 levels, despite
an elevated TSH,
• as they remember to take medication for a few days before testing;
• this is sufficient to normalize T4, but not TSH levels.
• Because T4 has a long half-life (7 days),
• who miss a dose can be advised to take two doses of the skipped tablets at
once.

45. • Other causes of increased levothyroxine requirements must be
excluded,
• particularly malabsorption (e.g., celiac disease, small-bowel surgery, atrophic
or Helicobacter pylori–related gastritis,), oral estrogen containing medications
or selective estrogen receptor modulator therapy, ingestion with a meal, and
drugs that interfere with T4 absorption or metabolism such as bile acid
sequestrants, ferrous sulfate, calcium supplements, selevamer, sucralfate,
proton pump inhibitors, lovastatin, aluminum hydroxide, rifampicin,
amiodarone, carbamazepine, phenytoin, and tyrosine kinase inhibitors.

46. SUBCLINICAL HYPOTHYROIDISM
• By definition, subclinical hypothyroidism refers to biochemical evidence
of thyroid hormone deficiency in patients who have few or no
apparent clinical features of hypothyroidism.
• No universally accepted recommendations for the management of
subclinical hypothyroidism, but levothyroxine is recommended-
• if the patient is a woman who wishes to conceive or is pregnant, or
• when TSH levels are above 10 mIU/L.
• when TSH levels are below 10 mIU/L, a trial of treatment may be considered
when patients have suggestive symptoms of hypothyroidism, positive TPO
antibodies, or any evidence of heart disease.
• It is important to confirm that any elevation of TSH is sustained over a 3-
month period before treatment is given.

47. • Treatment
• a low dose of levothyroxine (25–50 μg/d) with
• Goal - normalizing TSH.
• If levothyroxine is not given, thyroid function should be evaluated
annually.

48. • Prior to conception
• levothyroxine therapy should be targeted to maintain a serum TSH in the
normal range but <2.5 mIU/L for hypothyroid women.
• Subsequently, thyroid function should be evaluated immediately after
pregnancy is confirmed and every 4 weeks during the first half of the
pregnancy, with less frequent testing after 20 weeks’ gestation (every
6–8 weeks depending on whether levothyroxine dose adjustment is
ongoing).
• The levothyroxine dose may need to be increased by up to 45% during
pregnancy.

49. • Women should increase levothyroxine from once daily dosing to nine doses
per week as soon as pregnancy is confirmed, to anticipate this change.
• Dosage should be closely monitored with a goal TSH in the lower half of the trimester-
specific normative range, if available, or <2.5 mIU/L.
• After delivery, levothyroxine doses typically return to prepregnancy levels.
• Pregnant women should be counseled to separate ingestion of prenatal
vitamins and iron supplements from levothyroxine.
• Elderly patients 20% less thyroxine than younger patients.

50. • In the elderly, especially patients with known coronary artery disease,
• starting dose of levothyroxine is 12.5–25 μg/d
• similar increments every 2–3 months until TSH is normalized.
• In some patients, it may be impossible to achieve full replacement despite
optimal antianginal treatment.
• Emergency surgery safe in patients with untreated hypothyroidism,
• although routine surgery in a hypothyroid patient should be deferred until
euthyroidism is achieved.
• Myxedema coma still has a 20–40% mortality rate,
• despite intensive treatment, and outcomes are independent of the T4 and
TSH levels.

51. Clinical manifestations
• Reduced level of consciousness,
• Sometimes associated with seizures,
• as well as the other features of hypothyroidism .
• Hypothermia can reach 23°C (74°F).
• hyponatremia
• Sepsis should also be suspected.
• There may be a history of treated hypothyroidism with poor compliance, or the patient may be previously
undiagnosed.
• Almost always occurs in the elderly
• Precipitated by factors that impair respiration,
• such as drugs (especially sedatives, anesthetics, and antidepressants), pneumonia, congestive heart failure, myocardial infarction,
gastrointestinal bleeding, or cerebrovascular accidents.
• Exposure to cold

52. Pathogenesis
• Hypoventilation leading to hypoxia and hypercapnia, plays a major role
• hypoglycemia and dilutional hyponatremia also contribute to the
development of myxedema coma.
• Levothyroxine
• Loading dose a single IV bolus of 200–400 μg, ,
• Followed by a daily oral dose of 1.6 μg/kg/d, reduced by 25% if
administered IV.

53. • If suitable IV preparation is not available, same initial dose of
levothyroxine can be given by nasogastric tube (although absorption
may be impaired in myxedema).
• Because T4 → T3 conversion is impaired in myxedema coma,
• there is a rationale for adding liothyronine (T3) intravenously or via nasogastric
tube to levothyroxine treatment,
• excess liothyronine has the potential to provoke arrhythmias.
• Liothyronine
• loading dose of 5–20 μg should be followed by 2.5–10 μg 8 hourly, with lower
doses for those at cardiovascular risk.

54. Supportive therapy
• To correct any associated metabolic disturbances.
• External warming
• indicated only if the temperature is <30°C, as it can result in cardiovascular collapse .
• Space blankets should be used to prevent further heat loss.
• Impaired adrenal reserve in profound hypothyroidism
• Parenteral hydrocortisone (50 mg every 6 h) should be administered.
• Ventilatory support with regular blood gas analysis is usually needed during the first
48 h.
• Hypertonic saline or IV glucose - severe hyponatremia or hypoglycemia;
• hypotonic IV fluids should be avoided because they may exacerbate water retention
secondary to reduced renal perfusion and inappropriate vasopressin secretion.
• The metabolism of most medications is impaired, and sedatives should be avoided if
possible or used in reduced doses.
• Any precipitating factors should be treated,
• including the early use of broad-spectrum antibiotics, pending the exclusion of infection.

55. REFRENCES
• Harrison’s_Principles_of_Internal_Medicine,_Twentieth_Edition_(Vol.
1_&_Vol.2
• Davidsons Principles and Practice of Medicine 23rd ed
• UpToDate

56. •THANK YOU