Patient presents with symptoms suggestive of Hashimoto's thyroiditis, including fatigue, weight gain, constipation, dry skin, and cold intolerance.  The patient reports a family history of autoimmune thyroid disease.  Physical examination reveals a slightly enlarged, non-tender thyroid gland.  Laboratory results demonstrate elevated thyroid stimulating hormone (TSH) levels with normal or low free thyroxine (free T4) levels.  Thyroid peroxidase antibodies (TPO antibodies) are positive, confirming the diagnosis of Hashimoto's disease.  Differential diagnoses considered included hypothyroidism due to other causes, subclinical hypothyroidism, and iodine deficiency.  Assessment indicates primary hypothyroidism secondary to Hashimoto's autoimmune thyroiditis.  The patient was educated on the chronic nature of Hashimoto's disease and the need for ongoing monitoring and management.  Treatment initiated with levothyroxine sodium, starting at a low dose to minimize potential side effects.  Patient advised on medication adherence and the importance of regular follow-up appointments to monitor TSH and free T4 levels, adjust medication dosage as needed, and assess for treatment efficacy.  Patient counseling included discussion of lifestyle modifications, including diet and exercise, to support overall health and well-being.  ICD-10 code E03.8 (Other specified hypothyroidism) and E06.3 (Autoimmune thyroiditis) are documented for medical billing and coding purposes.  Follow-up appointment scheduled in six weeks to reassess thyroid function and adjust levothyroxine dosage as clinically indicated.