Hypothyroidism increases parathyroid hormone. This can lead to histamine issues, bone issues, and atherosclerosis from calcification.
“According to our results, an increase in TSH levels seems to cause an increase in PTH levels. One possible explanation of this interesting coincidence is that TRH can also cause an increase in PTH levels. Another possible explanation is that increased TSH levels can affect the measurement of PTH levels in immunometric assays. Finally, hypothyroidism can elongate the biological half life of PTH.”
Low calcium, magnesium, and vitamin D intake also elevate parathyroid hormone (PTH). Vitamin K2 and a higher calcium-to-phosphate intake also help prevent soft tissue calcification.
Ref: Does an increase in TSH levels affect PTH levels?