HYPOTHYROIDISM. By:Dr.NAZIA MUKHTAR

Transcription

1 HYPOTHYROIDISM By:Dr.NAZIA MUKHTAR

2 INTRODUCTION Hypothyroidism results from deficient production of thyroid hormone or a defect in thyroid hormone recepter activity. It may be congenital or acquired depending on cause and onset of disease.

3 FETAL &NEWBORN THYROID: Fetal T4 at term:11.5 ug/l Fetal T3 at term:45ng/l Fetal TSH at term:10 mu/l Acute TSH surge AT birth..conc reaches 60mU/L within 30 min in full term infants Next 5 days :10 Mu/L

4 CONGENITAL HYPOTHYROIDISM Incidence is 1 per 4000 live births. Twice as many girls as boys are affected. Menifestation may be right from birth or may present later in life depending upon etiology and extent of deficiency. Delay in presentation may also be due to partial compensation by transplacental supply of maternal T4.

5 PRIMARY CONGENITAL HYPOTHYROIDISM: 1.DEFECTIVE THYROID GLAND DEVELOPMENT 85% HYPOPLASIA, APLASIA, ECTOPIA. *ectopic thyroid gland is the most common cause. *detected by ultrasonogram or radionuclide scan. *occasionaly associated with thyroglossal cyst.

6 2.IODINE DEFICIENCY(endemic goitre) Most common cause of hypothyroidism in developing countries. 3.DEFECTS OF THYROID HORMONE SYNTHESIS:10%(genetic mutations) Defects in thyroid peroxidase are common.its function is organification and coupling of iodides.

7 Pendred syndrome Important association of peroxidase deficiency.characterised by sensiorineural deafness and congenital hypothyroid goitre. other causes: iodide transport defect,tg synthesis defect,deiodination defects.

8 4. MATERNAL ANTIBODIES.5% Maternal Thyrotropin Blocking Antibodies(TRBAb) cause transient cong. Hypothyroidism. Seen in infants of mothers with autoimmune thyroid diseases like grave s and hashimotos Half life of antibodies is 21 days &remission occurs in 3-6 months.

9 5.MATERNAL MEDICATIONS: Iodides,radioiodine,propylthiouracil, methimazole,amiodarone. 6.DEFECTIVE THYROID HORMONE TRANSPORT.

10 7.THYROID HORMONE UNRESPONSIVENESS: Autosomal dominant disorder. Mutations in thyroid hormone receptor. Patients usually have goitre. Levels of T3 T4 markedly raised. Raised or normal TSH differentiates it from Graves disease. Increased association with attention deficit hyperactivity disorder.

11 CENTRAL(HYPOPITUITARY) HYPOTHYROIDISM 1.PIT1 & PROP 1 MUTATIONS: deficiency of TSH,PROLACTIN,GH,LH,FSH,ACTH. 2.TRH deficiency/unresponsiveness. 3.TSH deficiency/unresponsiveness.

12 THYROID FUNCTION IN PRETERM: Cord serum T4 IS DECREASED. Postnatal TSH surge is reduced. Complications of prematurity like RDS further decrease T4 levels. If complications resolve T4 levels return to normal within 6 weeks. Infants at 28 weeks of gestation are more at risk because of immaturity of hypothalamopituitary axis &may be regular candidates of temporary T4 replacement.

13 CLINICAL FEATURES: AT BIRTH: usually asymptomatic at birth due to maternal T 4. wide open ant & post fontanels may give the earliest clue. body length and weight are usually normal.

14 NEONATAL PERIOD: Prolonged physiologic jaundice. Feeding difficulties:lack of interest, sluggishness,choking spells while nursing. Respiratory difficultiesdue to large tongue,apneic spells,noisy respiration,nasal obstruction,rds. Resistant constipation,large abdomen,umblical hernia.

15 INFANCY & CHILDHOOD. Stunted growth Narrow and far apart parpebral fissures Swollen eye lids Mouth kept open with thick protruiding tongue Short thick neck with fat deposition at shoulders

16 .Broad hands with short fingers Dry scaly thick skin Myxedema of eye lids,hands and genitals Pale sallow complexion,carotinemia.thick scalp with coarse brittle and scanty hair. Cardiomegaly and silent pericardial effusions. Muscular hypotonia Delayed dentition Delayed dev milestones. Physical,mental and sexual growth retardation.

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20 Lab findings: Screening programs use measurement of T4 followed by TSH if T4 is decreased. T3 T4 decreased TSH raised in primary hypothyroidism, decreased in centeral causes. Care should be given to normal range for age of patient specially 1 st week of life THYROGLOBULIN:decreased in thyroid agenesis or TG synthesis defects.

21 RADIOLOGY: Radiographs show retardation of osseous development in 60% of cases. Absent distal femoral epiphysis. Decreased bone age. Beaking of 12 th thoracic and 1 st &2 nd lumbar vertebrae. Skull Xrays show large fontanels,wide sutures with intrasutural bone. Xray chest shows cadiomegaly and pericardial effusions.

22 ULTRASONOLOGY: Assessment of site size and location of thyroid gland. Cystic or solid nature of nodules. It may miss ectopic thyroid tissue. RADIONUCLIDE SCAN: Pinpoints the underlying cause,locates ectopic glands.

23 Failure to demonstrate any thyroid tissue means either agenesis,or an intact gland with TRBAb,or iodide trapping defects. Normally situated gland with normal radioiodine uptake indicates defect in thyroid hormone biosynthesis. GENETIC STUDIES needed to confirm various defects in synthesis of thyroxine.

24 TREATMENT OF CONGENITAL HYPOTHYROIDISM Oral levothyroxine is the treatment of choice. DOSE: IN NEONATES :10-15 ug/kg/day Childeren :4ug/kg/day Adults :2ug/kg/day MONITORING: T3 T4 and TSH should be monitored monthaly for first 6 months and 2-3 monthly till 2 yrs and dose adjusted. SIDE EFFECTS: Only related with overdosage. craniosynostosis and behavioral problems.

25 IODINE DEFICIENCY(ENDEMIC GOITRE) Most common cause of congenital hypothyroidism in developing countries. It consists of two overlapping syndromes NEUROLOGIC SYNDROME: mental retardation,deaf mutism,gaite disturbances,pyramidal signs e.g foot clonus, babinski s sign and patellar hyper reflexia.

26 Goitrous but Euthyroid Normal pubertal development and adult stature MYXEDEMATOUS SYNDROME Mentally retarded,deaf,with neurologic symptoms Delayed growth and sexual maturation, myxedema Absence of goitre Low T4, High TSH.USG shows thyroid atrophy

27 PREVENTION AND TREATMENT Single intramuscular i/m injection of iodinated poppy seed oil TO women prevents iodine deficiency during future pregnancies for about 5 years. This therapy given to myxedematous children younger than 4 yrs results in euthyroid state in 5 months..older children and adults respond poorly to this therapy.

28 These patients need thyroxine replacement. WHO program of salt iodization has reduced incidence of endemic iodine deficiency by 50%

29 PROGNOSIS Early diagnosis and treatment leads to normal linear growth and mental development. If treatment not started early,brain damage leads to poor prognosis If the onset is after 2 years of age prognosis is good even if treatment started late.

30 ACQUIRED HYPOTHYROIDISM incidence:0.3% AUTOIMMUNE CAUSES:6% Hashimotos disease polyglandular autoimmune syndromes I&II:Down,Turner,Klinefelter syndromes and celiac diseases or diabetes are at more risk.

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32 IATROGENIC CAUSES ; Iodides,propylthiouracil,methemazole, Amiodarone irradiation, Radioiodine Thyroidectomy SYSTEMIC CAUSES: Cystinosis Langerhans cell hystiocytosis

33 CLINICAL FEATURES: Short stature/growth failure Cold intolerance Dry skin Cold peripheries Bradycardia Thin dry hair Pale,puffy eyes with loss of eyebrows

34 Goitre:typically firm and non tender Slow relaxing reflexes Constipation Delayed puberty Obesity Deterioration in school work Learning difficulties

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36 MENIFESTATIONS OF SEVERE COMPLICATED HYPOTHYROIDISM HEART FAILURE VENTILATORY FAILURE SIADH ILEUS HYPOTHERMIA AND LACK OF FEBRILE RESPONSE TO SEPSIS ADRENAL INSUFFICIENCY COAGULOPATHY

37 INVESTIGATIONS AND TREATMENT Same as congenital hypothyroidism Treat complications if present PROGNOSIS Complete resolution of symptoms seen after treatment except in long standing cases where normal growth limit can not be achieved even after treatment.

38 THANKYOU