Lithium (Greek, meaning Stone) was discovered by Arfwedson in 1811. 1 Lithium carbonate (Li 2 CO 3), salt form of lithium, is commonly used as a psychiatric medication for the treatment of mania, both acutely and in the long term. 2,3 The therapeutic uses of lithium also include use as an augmenting agent in depression, schizoaffective disorder, aggression, impulse control disorder, eating disorders, attention deficit disorder and in certain subsets of alcoholism. Lithium has been used in many medical disorders, especially cluster headache and dermatological disorders (seborrheic dermatitis, eczematoid dermatitis, genital herpes). 4 Initially, lithium was used to treat Urinary calculi and gout with little success, 5 till Cade J. (1949), 6 reported its antimanic effect. Lithium belongs to alkali group of metals, having atomic no.3 and atomic weight of 6.93. It is water soluble, non protein bound and is distributed in all body fluids. 7 Lithium is readily absorbed after oral administration and its peak level is reached in 2-4 hrs. About 95% of absorbed lithium carbonate is excreted in urine; about 1% in feces and 4-5 % in sweat. 2,8 Lithium binds poorly to high and low molecular weight plasma ABSTRACT Background: Lithium is routinely used to treat mania and other psychiatric disorders. It prevents the mood swing changes in bipolar disorders and the treatment is usually prolonged. Aim of current study was to observe histological changes in the thyroid gland of lithium carbonate treated albino rats. Methods: Sixty albino rats were taken and divided into two groups, group A (control group) of 15 animals, were fed with normal diet and group B of 45 animals, were fed normal diet along with lithium carbonate at the dose of 30mg/kg body weight daily. The animals were sacrificed at four, eight and twelve week's interval, 5µm sections prepared and stained with haematoxylin and eosin stain. Results: Microscopic changes in thyroid gland of albino rats were evident after 8 weeks of drug administration which include marked pleomorphism, shrinkage in size of thyroid follicles, excess of colloid and marked vacuolations in acini. At 12 th week of study, follicles were found both macro and micro follicular, with variable lining epithelium and hyperchromatic nuclei. Lining epithelium of some follicles was disrupted. The stroma was infiltrated with lymphocytes and eosinophils and there were some interfollicular hemorrhages. Conclusions: Lithium given over prolonged period will cause macro and micro follicular goiter with hyperplastic epithelium and hyper chromatic nuclei, hyperplasia of stroma with increased vascularity, sometimes hemorrhages and finally may lead to thyroiditis like picture. So, it is advised that patients on lithium therapy should be periodically evaluated for thyroid dysfunction
