Clinical trial with a double-blind, placebo-controlled, crossover design; enrolls approximately 30 euthyroid patients with benign thyroid nodules, who will receive for 6 weeks a spirulina-based supplement, and for another 6 weeks placebo. Thyroid ecography will be performed three times for each patient, and blood tests including TSH, free T4, free T3 and ceruloplasmin/Copper will also be performed 3 times for each patient. It is expected that a decrease in the thyroid nodules occurs with the supplement administration. Compared with placebo there will be a decrease of at least 20% in the volume or the largest diameter of the nodules during the 6-week administration of the supplement.

Clinical trial with double-blind, placebo-controlled, crossover design; enrolls approximately 30 euthyroid patients with benign thyroid nodules, who will receive for 6 weeks a spirulina-based supplement, and for another 6 weeks placebo.

• The sequence of administration supplement - placebo is unknown to the doctor or the patients
• The supplement and placebo are placed in identical capsules and vials by DVR Pharm
• The respective capsules are administered twice a day Thyroid ecography will be performed three times for each patient, and blood tests including TSH, free T4, free T3 and ceruloplasmin/Copper will also be performed 3 times for each patient.
• Echography and blood tests will be performed for each patient initially, after 6 weeks, and after 12 weeks It is expected that a decrease in the thyroid nodules occurs with the supplement administration.
• there will be a direct comparison of the nodules dimensions on the ecographic examinations, in millimeters, and of the blood levels of the molecules which reflect thyroid function

Inclusion Criteria:

• euthyroid adults (normal TSH)
• no criteria for malignancy is present (size, fine needle aspiration, lymph nodules)
• no other medication/supplement administered for thyroid, no steroids, beta-blocker

Exclusion Criteria:

• suspicion of malignancy / shown
• autoimmune disease
• abnormal thyroid function
• Wilson disease
• contraception with intrauterine device

For the primary outcome we compared the effect of the AI vs P after the initial 6 weeks of the study (V1-V2). For this we combined the AI-AI sequence and AI-P sequence in one arm, and compared with the P-AI sequence arm.

6 months

One patient who was on multiple medications at enrollment developed a generalized skin eruption with moderate prurit after a few days with the study substance; she interrupted the administration after talking with the investigator and afterwards it was revealed that she was taking placebo All participants who completed the study (n=34) received the AI (active ingredient) and 5 patients out of the 34 (n=29) received the AI-AI sequence, so that only 29 patients received placebo (P)