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THYROID GLAND (HYPERTHYROIDISM (CLINICAL MANIFESTATION (SYSTEMIC (anxiety,…
THYROID GLAND
HYPERTHYROIDISM
- due to either local or diffuse overproduction of thyroid hormone.
- More than 95% of cases are due to Graves disease, an autoimmune disorder that occurs in a geneticall- predisposed population. There is a strong female predisposition (6-8 :1)
- Graves disease is much less common in children than in adults, although it can occur at any age, especially in adolescence and in children with other autoimmune diseases
CLINICAL MANIFESTATION
SYSTEMIC
- anxiety, restlessness, increased appetite, sweating, diarrhoea, weight loss, rapid growth in height, tremor, tachycardia, wide pulse pressure, warm, vasodilated peripheries, goitre, learning difficulties/behaviour problems, psychosis
EYE SIGNS
- exophthalmos, ophthalmoplegia, lid retraction, lid lag
LABORATORY EVALUATOIN
- levels of thyroxine and/or tri-iodothyronine are elevated, TSH levels are suppressed to very low levels.
- In some cases, patients who have clinical signs of hyperthyroidism but who have normal levels of TSH and T4 may have isolated elevations of T3, so-called T3 toxicosis.
THERAPY
- MEDICAL – the first line treatment withcarbamazole or propylthiouracyl (interfere withthyroid hormone synthesis). It is given for about2 years. 40-75% relapse.
- SURGERY – subtotal thyroidectomy
- RADIOIODIDINE
HYPOTHYROIDISM
- insufficient secretion of thyroid hormones by the thyroid gland.
CONGENITAL
- PRIMARY (aplasia, hypoplasia of the thyroid gland) – common
- SECONDARY (TSH deficiency) –rare
- TERTIARY (TRH deficiency)-rarest
- is the commonest treatable cause of mental retardation.
CAUSES
- THYROID DYSGENESIS (80-85 % of CH)
- INBORN ERRORS OF THYROID HORMONOGENESIS (10-15 % of CH)
- IODINE DEFICIENCY: common worldwide but rare in Europe
- SECONDARY and TERTIARY HYPOTHYROIDISM: hypothalamic abnormality, associated with midline facial/brain dysmorphism, pituitary abnormality
SCREENING
- to achieve optimal neurological outcome, treatment must be initiated soon after birth
- Measurement of T4 and/or TSH
- Babies whose initial TSH is>50 mU/L are more likely to have permanent CH
- TSH between 20 and 49 mU/L is frequently a false positive or represents transient hypothyroidism
(common in premature infants in borderline iodine -deficient areas)
CLINICAL MANIFESTATION
- failure to thrive
- feeding problems
- prolonged jaundice
- delayed passage of stools
- pale, cold, mottled dry skin
- large tongue
- hoarse cry
- facial puffiness
- umbilical hernia
- goitre (occasionally)
- delayed development
THYROID HORMONE ACTION
- Stimulation of thermogenesis, caloriogenesis, water and ion transport
- Acceleration of substrate turnover, and amino acid and lipid metabolism
- Augmentation of the beta-adrenergic system
- Unique to children and infants is the stimulation of growth and development of various tissues, including the brain and skeleton
- Essential for neonatal brain growth
JUVENILE HYPOTHYROIDISM
- chronic lymphocytic thyroiditis (CLT)
- congenital abnormality (dysgenesis, dyshormonogenesis)
- iodine deficiency (endemic goitre)
- drugs or goitrogenes (cassava, water pollutants, cabbage, sweet potatoes, cauliflower, broccoli, soya)
- surgery
- radiation
-
ACQUIRED HYPOTHYROIDISM
CLINICAL MANIFESTATION
- short stature/growth failure
- slow-reflexes
- constipation
- delayed puberty
- obesity
- cold intolerance
- dry skin
- cold peripheries
- bradycardia
- pale, puffy eyes with loss of eyebrows
- learning difficulties
- goitre
laboratory evaluation
- Measurement of TSH is the best initial screen for primary hypothyroidism
- If the TSH is elevated, measurement of thyroxin will distinguish whether child has compensated (normal fT4) or overt (low fT4) hypothyroidism.
- A hypothalamic vs. a pituitary origin of the hypothyroidism may be distinguished by TRH testing.
- CLT is diagnosed by elevated titres of Tg and/or TPO Abs
- Thyroid ultrasonography and/or scintigraphy may be performed if Ab tests are negative or if a nodule is palpable.
HYPOTHYROIDISM-THERAPY
- Congenital hypothyroidism - replacement therapy with L-T4 should begin as soon as the diagnosis is confirmed. An initial dose of 12 ug/kg per day is recommended to normalize the T4 as soon as possible.
- Acquired hypothyroidism – a good starting dose is 3-4 ug/kg per day
- Thyroxine should be taken before eating at a consistent time of day
- Liquid preparations are unstable and should not be used.
ASYMPTOMATIC GOITRE
- Goitre occurs in 4-6% of schoolchildren in iodine-sufficient areas.
- There is a female preponderance (female-male ratio 2-3:1).
- Euthyroid goitres are most common.
- The most frequent cause of asymptomatic goitre is CLT.
THYROID NODULES
- uncommon in the first two decades of life in iodine-sufficient populations.
- Follicular adenomas and colloid cysts account for the majority of them, but they are more likely to be carcinomatous than are similar masses in adults.
- The most common form of cancer is papillary thyroid carcinoma.
- Thyroid hormone initiates its action by binding to specific receptors located in the cell nucleus.
- The binding of T3 to the thyroid hormone receptor (TR) is 10 times higher than T4.