Final answer:
The primary function of Eutroxsig (Levothyroxine) (thyroxine) is thyroid hormone replacement, specifically for the treatment of hypothyroidism.
Step-by-step explanation:
The primary function of Eutroxsig (Levothyroxine) (thyroxine) is B) Thyroid hormone replacement. Eutroxsig is a medication that contains the thyroid hormone thyroxine, which is used to treat hypothyroidism. Hypothyroidism is a condition where the thyroid gland does not produce enough thyroxine, resulting in symptoms such as fatigue and weight gain. By taking Eutroxsig, thyroid hormone levels can be restored to normal, alleviating the symptoms of hypothyroidism.