Hypothyroidism; This spontaneous case was reported by a patient and describes the occurrence of HYPOTHYROIDISM (Hypothyroidism) in a  patient of an unknown age and gender who received mRNA-1273 (Moderna COVID-19 Vaccine) for COVID-19 prophylaxis.     No Medical History information was reported.    On 28-Jul-2021, the patient received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) 1 dosage form. On an unknown date, the patient experienced HYPOTHYROIDISM (Hypothyroidism) (seriousness criterion medically significant). At the time of the report, HYPOTHYROIDISM (Hypothyroidism) had not resolved.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): In August 2021, Blood test: everything was fine.         No concomitant medication was reported.  The patient was wondering and did lots of reading and research on Moderna's take on thyroid issues after receiving the vaccine. Patient never had thyroid issues before and now, after reading multiple articles, it was all pointing to the vaccine.  Patient is a bodybuilder and could not cut the body weight to save the life. On March 2022, it went up by 2 whole points. The patient was on medications but were not helping for the condition.  Company Comment: This spontaneous case concerns a patient, of unknown age and gender, with no medical history reported, who experienced the unexpected, serious (medically significant) event of hypothyroidism. The event occurred unknown number of days after receiving the second dose of the mRNA-1273 vaccine. On an unspecified date in Aug2021 (unspecified number of days after vaccination), it was reported that the patient had a blood work (unspecified) done and 'everything was fine'. No additional details were provided until approximately 7 months after vaccination, an unspecified test result showed that 'it went up by 2 whole points'. No further details were provided regarding symptoms, consultation and specific laboratory test results. However, it was reported that the patient have 'hypothyroidism' and unspecified medications were 'not helping'. The event had not resolved at the time of the report. The benefit-risk relationship of the mRNA-1273 vaccine is not affected by this report.; Sender's Comments: This spontaneous case concerns a patient, of unknown age and gender, with no medical history reported, who experienced the unexpected, serious (medically significant) event of hypothyroidism. The event occurred unknown number of days after receiving the second dose of the mRNA-1273 vaccine. On an unspecified date in Aug2021 (unspecified number of days after vaccination), it was reported that the patient had a blood work (unspecified) done and 'everything was fine'. No additional details were provided until approximately 7 months after vaccination, an unspecified test result showed that 'it went up by 2 whole points'. No further details were provided regarding symptoms, consultation and specific laboratory test results. However, it was reported that the patient have 'hypothyroidism' and unspecified medications were 'not helping'. The event had not resolved at the time of the report. The benefit-risk relationship of the mRNA-1273 vaccine is not affected by this report.