Introduction

The role of thyroid hormone is vital in the timing and pace of development of central nervous system of our body during intrauterine life and in the early infancy. If there is a deficiency of thyroid hormone, it will greatly influence the growth of the cerebral and cerebellar cortex, proliferation of axons and branching of dendrites, myelinization and cell migration. Deficiency of thyroid hormones during neural differentiation results in severe and permanent modifications in the morphology and function of the nervous system, in particular a general slowing of cognitive functions with memory impairment and apathy.^[1]

One of the manifestations of the hypothyroidism is the peripheral neuropathy. The development of this neuropathy is insidious in onset, which will take a long period of time for clinical manifestations.^[2] The severity of the neuromuscular signs and symptoms depends on duration and severity of hormonal deficiency and clinical, electrophysiological and morphological improvement with hormone replacement therapy is typical.^[3-5]

1. Moosa A, and Dubowitz V. Slow nerve conduction velocity in cretins. Archeves of Disease in childhood, 1971, 48, 852.
2. Peter D Donofrio, In: Clinical Approach to a patient with Peripheral Neuropathy, Text book of Peripheral Neuropahy, 2012, Demos Medical Publishing.Pg-1.
3. Amato A.A.: Endocrin Myopathies and Toxic Myopathies. Ed: Brown William F., Bolton Charles F., Aminof Michael J, 2002.: Neuromuscular Function and Disease. Basic, Clinical and Electrodiagnostic Aspects, Vol. 2, 78:1399-1402, W.B. Saunders Company, Philadelphia
4. Latov N. Peripheral Neuropathies. Ed: Rowland L,P, 1995. Merritt’s textbook of neurology. Williams & Wilkins,649-676.
5. Palumbo C.F., Szabo R.M., Olmsted S.L., Sacramento C.A, 2000.: The effect of hypothyroidism and thyroid replacement on the development of carpal tunnel sydrome. J Hand Surgery., 25(4):734-739.
6. Nazliel, Bijen MD, Ylmaz, Murat MD, Gokce, Mustafa MD, Yetkin ,Ilhan MD, Baysal, Ali Ihsan. Blink Reflex in Hypothyroidism. Endocrinologist. 2007;17:144-47.
7. Ozkardes A, Ozata M, Beyhan Z, Corakci A, Vural O, Yardim M, et al. Acute hypothyroidism leads to reversible alterations in central nervous system as revealed by somatosensory evoked potentials. Electroencephalogr Clin Neurophysiol. 1996;100:500-4.
8. Ladenson PW, Stakes JW, Ridgway EC. Reversible alteration of the visual evoked potential in hypothyroidism. Am J Med. 1984;77:1010-4.
9. Kececi H, Degirmenci Y. Hormone replacement therapy in hypothyroidism and nerve conduction study. Neurophysiol Clin. 2006;36(2):79–83.
10. El-salem K, Ammani F. Neurophysio-logical changes in neurologically asymptomatic hypothyroid patients: a prospective cohort study. J ClinNeurophysiol. 2006;23(6):568–72.
11. Yeasmin S , Begum N, Befum S, Rahman SMH. Sensory Neuropathy in Hypothyroidism: Electrophysiological and Clinical Findings. Journal of Bangaladesh Society of Physiology.2007 Dec ;( 2):1-6.
12. Somay G, Oflaxoglu B, Us O, Surardamar A. Neuromuscular status of thyroid diseases: a prospective clinical and electrodiagnostic study. ElectromyogrClin Neurophysiol.2007 Mar-Apr; 47(2):67-78.
13. Gulbun Yuksel, Geysu Karlikaya, Tulin Tanridag, Onder US, Gulseren Akyuz. Nerve Conduction Studies, SEP and Blink Reflex in 103 recently diagnosed, Untreated Thyroid Disease Patients, Journal of Neurological Sciences 2007, volume 24, Number 1, Page 007-015.
14. Marcia W .Cruz; Mauro Tendrich, Mario Vaisman, Sergio A.P. Novis. Electroneuromyography and neuromuscular findings in 16 primary hypothyroid patients; Arq Neuropsiquiatr 1996, 54(1): 12-18.
15. Ruurd F Duyff, Joan Van den Bosch, D Martin Laman, Bert-Jan Potter van Loon. Neuromuscular findings in thyroid dysfunction: a prospective clinical and electrodiagnostic study. Journal of Neurology, Neurosurgery, Psychiatry 2000;68:750-755.
16. Pollard JD, McLeod JG, Honnibal TGA, Verheijden MA. Hypothyroid polyneuropathy. J NeurolSci 1982;53:461-71
17. Yuksel e. Somatosensory evoked potential and Blink reflex in newly diagnosed and untreated thyroid disease patients. Journal of Neurology, Neurosurgery, Psychiatry 2000; 68:850-855.
18. Raffaello Nemni , Edo Bottacchi, Rarraella Fazio, Angelo Mamoli, Massimo Corbo, Massimo Camerlingo, Giuseppe Galardi , Luciano Erenbourg, Nicholas Canal. Polyneuropathy in hypothyroidism: clinical, electrophysiological and morphological findings in four cases. Journal of Neurology, Neurosurgery and Psychiatry 1987; 50: 1454-1460.

Dr Garima Bafna

Senior Professor, Dept. of Physiology, J.L.N. Medical College, Ajmer, Rajasthan, India