NEONATAL GOITER

      What is goiter?
  ·         Goiter refers to enlargement of the thyroid gland; the most accurate method to determine thyroid gland volume is by ultrasonography.
  ·         The volume of each lobe is calculated from measurements of the depth (d), width (w),                             and length (l) of each lobe by the formula: V (mL) = d × w × l (cm) × 0.52.
  ·         The thyroid volume is the sum of both lobes; the volume of the isthmus is not included.
  ·         Thyroid volume should then be compared with reference ranges for age to determine if it                         is normal or enlarged.
 
2.             What are the mechanisms?
The newborns can present with goiter which can be a visible or palpable swelling or may be not visible or palpable but can be identified by USG examination.
·         Increased thyroid-stimulating hormone (TSH) secretion, resulting from hypothyroidism, in which TSH acts as a thyroid growth factor.
·         Activation of TSH receptors, which result in thyroid hyperplasia and increased thyroid hormone secretion. This may be caused by TSH receptor-stimulating antibodies (as in Graves disease) or by genetic mutations that activate the TSH receptor.
·         TSH-independent processes, such as inflammation associated with thyroiditis, benign and malignant tumors, or infiltrative diseases.
 
3.      What are the causes of nenatal goiter?    

            Causes Of Neonatal goiter are

·         Adminstration of antithyroid drugs to mother.
·         Maternal Graves disease
·         Radioactive iodine to mother during pregnancy
·         Intrinsic thyroid defect in newborns
·         Other iodine containing medications like amiadarone.
·         Neonatal Graves disease.
 
4.      How administration of maternal antithyroid drug causes neonatal goiter?
·         Administration of drugs decreases T3 and T4 which stimulates TSH secretion which acts on thyroid follicules  causing thyroid follicular hyperplasia along with increase Tg synthesis.
 
5.      How maternal Graves disease cause neonatal goiter?
·         The TRABs stimulate TSH receptor in thyroid of newborn by transplacental transfer of Abs from mother to fetus
·         These children usually present with features of neonatal graves.
·         If maternal graves is under treatment the antithyroid drugs can cross placenta and cause hypothyroidism and goiter.
 
6.      Can maternal autoimmune thyroid disease cause neonatal goiter?
·         Yes. It can.
·         If the mother has autoimmune thyroid disease, which is the most common cause of acquired hypothyroidism, the infant's goiter may be caused by transplacental passage of a TSH receptor antibody. In this setting, the infant's goiter is caused by a TSH receptor-stimulating antibody, or a combination of a TSH receptor-stimulating and -blocking antibody, where the stimulating antibody predominates, and causing hyperthyroidism.
 
If TSH R blocking Ab predominates hypothyroidism with small thyroid gland occurs.
 
7.      What are common intrinsic defects of thyroid causing neonatal goiterr?
·         Dyshormonogenesis
 
8.      What to suspect when unilateral neonatal goiter is present?
·         Unilateral agenesis of thyroid and rarely tumors like teratoma.
 
9.      What are the clinical features of neonatal goiter?

·         Diffusely enlarged and symmetrical gland with respiratory distress may occur.
Newborns may be hypothyroid or hyperthyroid.
 
10.  What is the result of TFT in neonatal goiter?
 
·         Hyperthyroid or hyperthyroid.
 
11.  How to proceed with thyroid antibody tests in neonatal goiter?

12.       When should be evaluate for iodine in neonatal goiter?

·         If there is suspicion of iodine excess causing goiter we can do a 2 hour urinay iodine estimation.
 
13.      When should we do a radionuclide scanning in neonatal goiter?

·         It is usually done in case we suspect dyshormonogenesis as a case of goiter when all other possibilities have been rules out.
 
14.      What do we get in radionuclide scanning?
·         Increase in iodine uptake except for NIS receptor defect.
 
15.      How can McCune Albright syndrome cause neonatal goiter?
·         McCune-Albright syndrome is caused by somatic activating mutations of the TSH receptor G protein stimulatory alpha subunit.
 
·         These mutations result in thyroid hyperplasia or formation of nodules and, ultimately, in toxic nodular goiters.
 
·         The goiter may be present in infancy, but more commonly, patients present later in childhood with toxic multinodular goiter. Affected patients also may present with precocious puberty.
 
16.      How can thyroid hemi agenesis present with neonatal goiter?
·         Due to compensatory enlargement  of normal thyroid lobe. These patients are usually euthyroid.
 
17.      How do we treat a case of neonatal goiter due to maternal antithyroid drugs?
·         The transplacentally transferred drugs are usually metabolized within 7-10 days and thus no treatment of hypothyroidism is required.
 
18.      How do we treat a case of neonatal goiter with respiratory distress?
·         Thyroidectomy rather than tracheostomy.
 
19.      What is intratracheal neonatal goiter?
·         In some rare cases the thyroid gland can be ectopically located within the trachea which can be continuous with eutopically located thyroid.
·         This ectopic thyroid tissue can undergo goitrous change causing airway obstruction.
 
20.      How to treat an intratracheal neonatal goiter?
·         Mild cases – levothyroxine will decrease the size
·         In severe cases with severe obstruction surgery is required