Pediatrics 5th year, 12th lecture (Dr. Jamal)

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The lecture has been given on Feb. 13th, 2011 by Dr. Jamal.

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Pediatrics 5th year, 12th lecture (Dr. Jamal)

  1. 1. Thyroid gland disordersHypothyroidism;Congenital hypothyroidism is important because; 1- It is easily screenable. 2- Easily treatable. 3- Relatively common (one/5000) 4- Permanent intellectual defects& short stature occur from delayed diagnosis& or inadequate treatment.Clinical features:Affected babies look normal at birth, but days-weeks after birth features like sleepiness, poorfeeding, prolonged jaundice, constipation & hoarse cry appear.Detectable signs on examination include: lethargy, jaundice, large tongue, goiter ( rarely ).The skin is rough, cold, dry, mottling& thick. Coarse facies, abdominal distention, umbilicalhernia, wide posterior fontanel ( more than 0.5cm.), hypothermia, peripheral cyanosis,edema, thick lips, puffy eyelids, pallor, wrinkled forehead with a low hairline& sparseeyebrows. In addition the neck is short with a pad of supraclavicular fat. The scalp hair isscanty, rough, dry& brittle. Diagnosis:A high degree of suspicion is essential to make early diagnosis and thus avoid intellectualimpairment.S.T4 & TSH are both measured.In the majority of cases T4 is low & TSH is high (primary) while both may be low (insecondary).Knee x-ray (shows lower femoral and upper tibeal epiphysis in normal full term babies).Absence of these centers in full-term babies indicates delayed Bone Age.Elevated S.cholesterol.Elevated S.alk.phosphatase.Low voltage ECG.Isotope & thyroid U.S studies are some times helpful.Prevention:Hypothyroidism is included in the neonatal screening program applied in most parts of theworld. 10% of cases may still be missed by this screening test as the test detects high TSH.Treatment:Oral synthetic thyroxine is the standard drug of choice. Small doses are started e.g. 25micro-gm. then gradually increased to therapeutic levels, this varies from one child to another ,generally the ultimate daily requirement will range between 50 micro-gm & 300micro-gm,given in one dose at morning .The aim is to 1.Start as soon as possible. 2. Continue treatment indefinitely. 3. Keep T4 level in the blood within upper half of normal range 4. Keep the patient asymptomatic regarding thyroid status. 1
  2. 2. Acquired hypothyroidism;This is much rarer than the congenital form & is usually of insidious onset.Etiology:Causes of primary acquired form: - iodine deficiency - autoimmune (Hashimotos) thyroiditis - thyroid surgery - following irradiation - radioiodine therapy - Antithyroid therapy - Goiterogens as iodide, cabbage & soya beans.Causes of secondary & tertiary forms; - Craniopharyngioma - Neurosurgery - Cranial irradiationClinical features:the principal features include : weight gain , tiredness , pallor , cold dry skin ,myxoedematous facies , short stature , constipation , poor school performance , goiter ,slipped femoral epiphysis & delayed puberty.Investigation:Decrease T4 & increase TSH in primary form.Thyroid antibodies are detected in autoimmune thyroiditis.Thyroid scan may help in diagnosis of late presentation of thyroid dysgenesis.Skeleton radiography shows both delayed bone age & epiphysial dysgenesis.In fact proper study of the later may indicate the age of the onset of the hypothyroid state.Low or normal TSH & decrease T4 is suggestive of secondary and tertiary hypothyroidism, itcan be further investigated by TRH test +/_ cranial CT & or MRI.HyperthyroidismThis is extremely rare in comparison to hypothyroidism.causes: 1. Gravis disease. 2. Neonatal thyrotoxicosis. 3. Hashomotos thyroididtis. 4. Syndrome of selective T4 resistance. 5. Autonomous nodules.Features:Irritability, weight loss in spite of increased appetite, palpitation, heat intolerance, sleepdisturbance, diarrhea, goiter (usually diffuse), exophthalmos (rarely with ophthalmoplegia)increased P.R., tremor, murmur & thyroid bruit.Trasient neonatal thyrotoxicosis may occur following transplacental transfer of maternalthyroid stimulating immunoglobulin.Investigation; 2
  3. 3. - Increased T4 & T3 ( rarely T3 alone) & decrease TSH - Increased TSH receptor antibodies - Positive thyroid antibodies - Advanced bone ageTreatment:The 3 modalities include 1. medical ( carbimazole+ propranolol) 2. radioactive iodine 3. surgical Parathyroid disordersParathormone (PTH) helps in maintaining normal S.calcium level by releasing calcium fromthe bone & reabsorbing calcium from the kidneys.PTH also releases phosphorus from the bone & excretes phosphorus from the kidney.In addition PTH increases calcium absorption from the gut.Hypoparathyroidism may result from congenital absence of parathyroids which whenassociated with aplasia of thymus, CHD& immune-deficiency, it is named DiGeorgesyndrome.Transient hypoparathyrodism may occur in neonates with resultant hypocalcemia, as aresult of intake of high phosphate/calcium ratio.Autoimmune hypoparathyroidism is usually seen in association with Addison disease,pernicious anemia, cellular immune-deficiency, alopecia aerata & steatorrhea.Psudohypoparathyroidism (parathyroid resistance) on the other hand is a rare, possiblyA.D. disorder, presents with short stature, short metacarpals, developmental delay& elevatedS.parathormone level.Hyperparathyroidism is an extremely rare disorder, characterized by hypercalcemia,hypophosphatemia& hypercalcurea. Adrenal gland disordersAdrenal cortex secretes a number of steroid compounds which help in maintenance ofelectrolyte balance, carbohydrate& protein metabolism, growth& in stimulation of sexualdevelopment, through secretion of mineralocorticoids, glucocorticoids& androgens.Glucocorticoid& androgen synthesis are regulated by a negative feed-back on ACTH, whilemineralo-corticoid synthesis is controlled by the renin-angiotensin system & is independenton ACTH, (thus normal S. potassium in 2ndary adrenocortical insufficiency)On the other hand adrenal medulla secrets adrenaline& noradrenaline which help inmaintinence of B.P., regulation of H.R& peripheral resistance.Adrenocortical insufficiency:Causes: 1- Prolonged steroid therapy or tumors (e.g. craniopharyngioma) in the region of pituitary causing pituitary gland destruction & decreased ACTH secretion. 2-Congenital adrenal hypoplasia. 3-Adrenal hemorrhage or necrosis in septicemic illnesses as meningococcemia (Waterhouse-Friderichsen syndrome). 4-Chronic adrenocortical failure (Addison disease) may occur in T.B. or as an autoimmune process. This later form may occur alone or occurs in association with other 3
  4. 4. auto-immune manifestations& endocrine gland involvement as thyroid, parathyroid orbeta cells of pancreas. Adrenoleucodystrophy is an XLR disorder of fatty acid metabolism characterized byadrenal insufficiency& progressive neurological dysfunction.Clinical picture:Symptoms of adrenocortial insufficiency usually appear gradually as weakness, nausea,vomiting, weight loss& salt craving.Physical findings include; postural hypotention, increased pigmentation over joints, lips,gums, scars, nipples. This over pigmentation is because MSH is a by-product of ACTHbiosynthetic pathway.On the other hand adrenocortical insufficiency may occur acutely (adreno-cortical crisis)giving rise to fever, vomiting, hypotention, hypoglycemia, dehydration & shock.This crisis usually precipitated by intercurrent illnesses, surgery& trauma.Investigations show:Decreased S. sodium while increased S.potassium (in the primary form).Decreased S.Cortisol & decreased S. ACTH (in secondary).Treatment:Addison crisis require urgent treatment by I.V. Normal saline in 5% dextrose, in additionto I.V. Hydrocortisone followed by oral cortisone& mineralocorticoids.Cortisone dose should be increased during stress periods. Adrenal gland hyperactivityThis condition comprises:1-Cushing syndrome& disease.2-Congenital adrenal hyperplasia (adrenogenital syndrome).3-Hyperaldosteronism.4-Adrenal medulla hyperactivity, which include: a- Pheochromocytoma. b- Neuroblastoma. c- Ganglioneuroma (benign)Cushing syndrome (C.S.): This is a group of features that result from high cortisollevels& is due to either endogenous overproduction or exogenous steroid administrationin pharmacological doses.Manifestations of C.S. include; moon face, truncal obesity, abdominal striae, acne, slowgrowth, delayed bone age, hypertention& muscle weakness.Cushing disease; on the other hand is the most common form of C.S. in older children&in most cases it is caused by increased ACTH secretion from a microadenoma of thepituitary.Investigations reveal;Raised S. cortisol.Increased 24- hour urine free cortisol.Dexamethason suppression test shows failure of increased cortisol secretion. 4
  5. 5. Disorders of Hypothalamus& pituitary gland:Hypothalamus produces five known releasing factors which regulate the pituitary. In additionit produces 2 hormones, namely Vasopressin (ADH) & Oxytocin.The pituitary gland produces several hormones which are: -Growth hormone: deficiency of which produces pituitary dwarfism& rarely Frohlichsyndrome (obesity, hypogonadism, short stature& diabetes insipidus), while excess growthhormone secretion produces gigantism (before puberty) & acromegaly (after puberty). -TSH; deficiency of which causes secondary hypothyroidism, while it’s excess results insecondary hyperthyroidism. - ACTH; deficiency of which is rarely absolute& causes adrenocortical insufficiency,while it’s excess results in Cushing syndrome. - Prolactin; Helps in initiation& maintenance of lactation. Secretion of prolactin isregulated by babies sucking of the nipple. - Gonadotrophins, which include FSH& LH.FSH in female helps in growth of ovarian follicle. FSH deficiency results in amenorrheawhile its excess causes precocious puberty.On the other hand in males FSH helps in gametogenesis. -L.H.; in female LH helps in lutenization& rupture of the follicles, while in males itstimulates testosterone secretion. Growth hormone deficiency Causes: 1- Congenital (genetic or developmental defects). 2- Acquired; tumors especially craniopharyngioma, vascular, cranial irradiation, infective, infiltration, traumatic & autoimmune. In general the commonest form of GH deficiency is decreased pituitary secretion; hypothalamic dysfunction is less common while target cell failure is the least common. GH deficiency occurs at a rate of 1 in 10.000 & is 4 times more common in boys. Clinical picture: Congenital form may present in the neonatal period as hypoglycemia, but the most common presentation is during childhood as for short stature with normal body proportion. Other physical manifestations include; central obesity, younger looking doll- like facies, frontal bossing, small penis& scrotum, relatively small hands& feet, delayed teething, high pitched voice& delayed puberty. Investigations: Height is usually below 3rd. centile. Delayed bone age. Growth velocity of less than 4 cm. / year during pre-pubertal period is highly indicative of G.H. deficiency. Decreased GH level (both basal& after provocation). 5
  6. 6. Differential diagnosis:GH deficiency should be differentiated from other forms of short stature, like:1- Constitutional delay in growth& puberty.2- Hypothyroidism.3- Malnutrition.4- Turner syndrome.5- GH insensitivity (Laron syndrome).6- Chronic systemic diseases.7- Genetic.8- Psychosocial deprivation.Treatment:GH subcutaneous injection, 0.1 I.U./kg/day until appropriate growth is attained (14-18years of age) 6

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