Levothyroxine is also contraindicated for people with uncorrected adrenal insufficiency, as thyroid hormones may cause an acute adrenal crisis by increasing the metabolic clearance of glucocorticoids. For oral tablets, the inability to swallow capsules is an additional contraindication. Side effects
Adverse events are generally caused by incorrect dosing. Long-term suppression of TSH values below normal values frequently cause cardiac side effects and contribute to decreases in bone mineral density (low TSH levels are also well known to contribute to osteoporosis).Too high a dose of levothyroxine causes hyperthyroidism. Overdose can result in heart palpitations, abdominal pain, nausea, anxiousness, confusion, agitation, insomnia, weight loss, and increased appetite. Allergic reactions to the drug are characterized by symptoms such as difficulty breathing, shortness of breath, or swelling of the face and tongue. Acute overdose may cause fever, hypoglycemia, heart failure, coma, and unrecognized adrenal insufficiency. Acute massive overdose may be life-threatening; treatment should be symptomatic and supportive. Massive overdose can be associated with increased sympathetic activity, thus may require treatment with beta-blockers.The effects of overdosing appear 6 hours to 11 days after ingestion. Interactions
Many foods and other substances  can interfere with absorption of thyroxine. Substances that reduce absorption are aluminium- and magnesium-containing antacids, simethicone, sucralfate, cholestyramine, colestipol, and polystyrene sulfonate. Sevelamer with calcium carbonate may decrease the bioavailability of levothyroxine. Grapefruit juice may delay the absorption of levothyroxine, but based on a study of 10 healthy people aged 20–30 (eight men, two women), it may not have a significant effect on bioavailability in young adults.
Hence it is not surprising that OWT therapy has not become popular and is very sparingly used across the globe. References
External links
"Levothyroxine". Drug Information Portal. U.S. National Library of Medicine. "Levothyroxine sodium". Drug Information Portal. U.S. National Library of Medicine. "Real-world Evidence from a Narrow Therapeutic Index Product (Levothyroxine) Reflects the Therapeutic Equivalence of Generic Drug Products". U.S. Food and Drug Administration (FDA). 19 November 2020.