<prompt> Which of the following is NOT essential for normal biosynthesis of thyroid hormoneIodineFerritinThyroglobulinTSH  <response>: Ferritin 319- Ganong22nd 360- K.S 4th 689. A.K. Jain 3rd 304-5- Ganong 23rd Iodine I2 is the raw material essential for thyroid hormone synthesis Total I entering ECF is 600igmday 500 40 60 of which, 120 mmgday 20 enters the thyroid and 480 mgday 80 is excreted in urine Normal TS ratio is 25-50:1 T4 deficiency during development causes mental retardation and molar rigidity and deafnessSynthesis of Thyroid hormonesSteps of synthesis of thyroid hormones1. Thyroglobulin synthesis2. Iodide trapping or iodide pump3. Oxidation of iodide4. Iodination of tyrosine5. Coupling reactionsTSH - secreted by anterior pituitary is the major factor regulating the synthesis and release of thyroid hormones.It is also necessary for the growth and secretory activity of the thyroid glands.TSH not only stimulate the secretion of stored thyroid hormones from follicular colloid but it also promotes synthesis of fresh thyroid hormones. 