THYROID DISORDERS:

HYPOTHYROIDISM

REFERENCES

1. Practice Guidelines for Thyroid DisordersThe Malaysian Consensus 2000Ministry of Health Malaysia

2. Oxford Handbook of Endocrinology & DiabetesHelen E. Turner, and John A.H. Wass1st edition, 2003

3. Update on the management of hyperthyroidism and hypothyroidism, Kenneth A. Woeber,, Arch Fam Med (2000) 9; 743-747

INTRODUCTION

• Hypometabolic state due to deficiency of thyroid hormones

• Accumulation of GAGs (mucopolysaccharides) in the SC tissue

• Incidence : mid-50s : male:female ratio → 1:10

ETIOLOGY

1. PRIMARY : THYROID FAILURE (95%)

2. SECONDARY : PITUITARY TSH DEFICIT

3. TERTIARY : HYPOTHALAMIC DEFICIENCY

OF TSH

4. PERIPHERAL RESISTANCE TO THE ACTIONS

OF THYROID HORMONES

• Autoimmune hypothyroidism:-Hashimoto’s thyroiditis- Atrophic thyroiditis

• Iatrogenic:-Radio-iodine therapy- Thyroidectomy- External radiation to the neck (lymphoma/CA)

• Drugs : -Antithyroid drugs, amiodarone, lithium, interferon

• Congenital hypothyroidism:-Thyroid agenesis- Dyshormogenesis- TSH-R mutation

PRIMARY CAUSES

• Iodine deficiency

• Infiltrative disorder

2°, 3° AND OTHER CAUSES

• Hypopituitarism (2°):– Tumour– Surgery– Radiation – Postpartum: Sheehan’s

syndrome

• Hypothalamic causes (3°):– Tumour– Trauma

• Peripheral resistance (rare)

LABORATORY INVX• Diagnosis : serum TSH

: serum T4 total or free?

: thyroid autoantibodies• In outpatient setting → serum TSH !!!

SUBCLINICAL HYPOTHYROIDISM:

• patient is not overtly

hyperthyroid

• serum free T4 is normal, but TSH is

↑

MANAGEMENT• Aim: to make patient euthyroid, clinically &

biochemically.

• Treatment with L-thyroxine is life-long → ensure compliance!!

• Monitoring:– Clinically & biochemically– Measure TSH and free T4 2-3 month after initiation of therapy →

determine maintenance dose

Continue..

1) OVERT HYPOTHYROIDISM– Starting dose : 50-100 ug/d →→ 100-200ug/d

within 2 weeks

– IHD / grossly hypothyroid / elderly:• Start at 25 ug/d• ↑ slowly within 2-4/52 according to pt response• Angina: withhold / ↓ dose. Proper mx of IHD

– Hypopituitarism:• Cortisol: to avoid adrenal crisis

2) SUBCLINICAL HYPOTHYROIDISM:– L-thyroxine to ↓ risk of CAD– 50-100 ug/d →→ adjust to maintain TSH at

normal level

3) PREGNANCY:– ↑ dose, especially in 2nd / 3rd trimester

EMERGENCY:MYXEDEMA COMA

• Severe, uncompensated form of prolonged hypoTH

• Precipitated by stress / infection / drug

• Complication:– Hypoventilation– Cardiac failure– Fluid & electrolyte imbalance– coma

PLAN OF MANAGEMENT

1. Treat precipitating cause2. Gradual rewarming → blanket3. Accurate core T° → rectal thermometer

– Aim for slow ↑ in core T° : 0.5 °C/hr4. Cardiac monitoring5. Correction of electrolyte abnormalities6. Adequate hydration & nutrition (dextrose)7. L-thyroxine (300-400 ug oral/iv) &

tri-iodothyronine 10 ug 8 hrly8. Hydrocortisone : blood cortisol

CONGENITALHYPOTHYROIDISM

• Incidence : 1 in 4000-5000 live births

• Importance of TH hormones:• Normal development of nervous system !!

• Features: – Prolonged jaundice– Poor feeding– Constipation– Unusually quite baby

Continue..

• Signs (if left untreated, appear at 3-6 months):– Coarse facies– Dry skin– Hoarse cry– Umbilical hernia – macroglossia– Delayed developmental milestones

MANAGEMENT• Newborn screening• Diagnosis confirmed → treat ASAP • Dose: start at 10-12 ug/kg/day• Aim : maintain TSH at normal level

: maintain free T4 at upper limit of normal range

• Life-long treatment: if transient hypoTH is suspected, re-evaluate at 2 years old.

• Monitoring: antropometry/milestones/bone age progression

THANKYOU