Normally most of the copper in your blood is carried by a protein called ceruloplasmin. Adults have 50 to 120 milligrams (mg) of copper in their body, mostly in muscle and the liver. Copper helps make melanin, bone, and connective tissue. It also helps with many other processes in your body.
Unlike most animals on earth, whose blood is iron-based, some mollusks (Mollusca) and arthropods (Arthropoda) have copper–based blood. While the best-known example of an arthropod with copper–based blood is the horseshoe crab, a number of other arthropods have blue blood.
Copper and iron are essential elements in the human organism, and recent enlightening research has given increased evidence of their importance in the blood stream.
https://jamanetwork.com/journals/jamainternalmedicine/article-abstract/549306
In our first experiments, nine years ago, on the iron content of whole blood, we found it necessary to establish a large series of determinations on normal persons.1 The average iron content of whole blood for 200 men was 50.13 ± 0.15 mg. per hundred cubic centimeters, and for 100 women it was 43.42 ± 0.19. The mathematical index, the mode, the figure which appears most frequently in the series of determinations and around which the majority of figures group themselves, was 50 mg. of iron per hundred cubic centimeters for 200 men and 45 mg. for 100 women.1b The fact that in women the average fell below the mode illustrates the tendency toward the anemic state in women.
Copper may be involved in the pathophysiology of depression. Clinical data on this issue are very limited and not conclusive. The purpose of the study was to determine the copper concentration in the serum of patients with major depressive disorder and to discuss its potential clinical usefulness as a biomarker of the disease. A case-control clinical study included 69 patients with current depressive episode, 45 patients in remission and 50 healthy volunteers. Cu concentration was measured by electrothermal atomic absorption spectrometry (ETAAS). The mean serum copper level in depressed patients was slightly lower (by 11 %; not statistically significant) than in the control group. Furthermore, there was no significant difference in Cu2+ concentration between depressive episode and remission, nor between remission and control group. In the remission group were observed significant correlations between copper levels and the average number of relapses over the past years or time of remission. There was no correlation between serum copper and severity of depression, as measured by HDRS and MADRS. The obtained results showed no significant differences between the copper concentration in the blood serum of patients (both with current depressive episode and in remission) and healthy volunteers, as well as the lack of correlations between the copper level in the active stage of the disease and clinical features of the population. Our study is the first conducted on such a large population of patients, so the results may be particularly important and reliable source of knowledge about the potential role of copper in depression.
https://pubmed.ncbi.nlm.nih.gov/27147437/