Hypothyroidism

1
Hypothyroidism

• Joy Ziradkar / Carl Robbins

• Common disorder
• Synthroid one of most commonly prescribed
  drugs in Canada
• Seven million prescriptions last year
• Rising at 12 per year (source CBC qq!!)

2
Thyroid

• Historical Notes
• Thyroid Thyreoeides Shield (Greek)
• Goiter Known since 2700 BC
• Thyroid gland Goiter relationship Hieronymus
  Fabricus 1619

3
Thyroid

• Anatomy
• Blood supply
• Bilobed / Mass 15 20
• Micro lobules / follicles
• Cells - cuboidal epithelial (TSH) and
  parafollicular (calcitonin)

4
Thyroid

• Physiology
• Hormones
• Calcitonin
• Thyroxine
• Iodination of tyrosine produces thyroxine (T4 /
  avg 125ug / day) and Tri-iodothyhtronin (T3)
• T4 and T3 bound to globulin / Only small
  fractions not bound are biologically active
• TSH - Glycoprotein released in response to
  hypothalamic TRH

5
Thyroid

• Pathology
• qualitative / quantitative alteration of function
  
• hypothyroidism - hypo metabolism
• hyperthyroidism - thyrotoxicosis
• enlargement
• generalized goiter
• focal usually benign or malignant neoplasm
• thyroxine deficiency

6
Thyroid Function

• Radioimmunassay
• T4, T3, TBG, TSH
• T3 resin uptake using I131 most common
• Isotope Imaging
• Ultrasonography
• Miscellaneous Tests
• Thyroid antibodies
• TSH receptor antibodies
• Plasma thyroglobulin level

7
Hypothyroidism

• Congenital
• Congenital Non-Goitrous Hypothyroidism
• Incidence 14000
• Decreased T4 Elevated TSH
• Newborn Screening critical
• Manage by thyroid replacement
• Congenital Goitrous Hypothyroidism
• Unusual / rare (1 30,000)
• Inborn error of metabolism

8
Hypothyroidism

• Acquired
• Hashimotos Thyroiditis
• Autoimmune cause
• lymphocytic thyroiditis
• Radioactive iodide ablation
• Surgical ablation
• Idiopathic
• Ectopic thyroid dysgenesis
• Goitrogens

9
Diagnosis hypothyroidism

• Do we really have to perform certain
  investigations before the management of
  hypothyroid?
• Dry skin
• Weight gain with decreased appetite / weakness
• Reflexes depressed ( Colbourne
  modification!)
• Hoarseness / hair loss / hypotension
• Thick hair with loss of lateral eyebrow hair
• Puffiness of face, proximal muscle weakness
• Constipation
• Intolerance to cold
• Bradycardia
• Tongue enlarged macroglossia
• Menorrhagia or Amenorrhea
• Obese
• Hypercholesterolemia, Hyperprolactinemia

10
Diagnosis hypothyroidism

• Laboratory / Imaging features
• Decreased T4, T3 Raised TSH
• Antimicrosomal antibodies, Antithyroglobulin
  antibodies present
• Skeletal maturation delayed indicative of
  duration of hypothyroidism

11
Management hypothyroidism

• Thyroid hormone replacement
• Synthetic l-thyroxine
• Start 1-2 ug/Kg /day single daily dose
• Titrate treatment against serum T4 and TSH aim
  for normal range
• Associated disorders that predispose to
  Hashimotos
• Diabetes Mellitus
• Adrenal Insufficiency
• Trisomy 21
• Turner Syndrome

12
Hypothyroidism

• Comments / Questions

13
Case One F 8

• Hx asthma required Rx
• FH mom hypothyroid, g-mom hyper
• Investigated because of FH
• Absence significant symptoms except some fatigue
• Symmetrically enlarged thyroid without nodules
• What is your approach to this patient?

14
Case Two - F 15

• Complaints of irregular periods and hirsuitism
• Associated fatigue and cold intolerance
• FH Hypothyroidism g-mom aunt
• Bulky, firm ? Nodular thyroid
• What is your approach to this patient?

15
Case Three F 46

• Complaints tiredness several months with
  depression and mood swings. Describes herself as
  anxious and tends to get worked up
• Irregular periods with menorrhagia for past six
  months
• Normal PE (clinically euthyroid)
• What is your approach to this patient?

16
Case Four M 39

• Hospital admission Angina / IHD
• Hx GERD and c/o fatigue
• PE - nodule in inf pole lobe thyroid
• What is your approach to this patient?

17
Case Five F 28

• No symptoms Periodic Health Check
• PE normal
• clinically euthyroid
• 3 cm nodule in (L) lobe of thyroid

18
Case Six F 56

• Complaints of hoarseness, weakness
• Five year previously presented with weight loss,
  heat intolerance, hyperactivity - Rx with
  radioactive iodine
• What is your approach to this patient?