In addition to endocrine glands, some organs whose functions are primarily nonendocrine also produce hormones. these endocrine tissues include and in addition to endocrine glands, some organs whose functions are primarily nonendocrine also produce hormones. these endocrine tissues include and parathyroids and skin gastrointestinal tract and adrenals adipose tissue and sweat glands heart and kidneys

In addition to endocrine glands, some organs whose functions are primarily nonendocrine also produce hormones. these endocrine tissues include heart and kidneys.  

The heart can act as an endocrine organ by releasing natriuretic peptides that lower the blood pressure. Those are an A-type natriuretic peptide (ANP) from the from stretched atria and B-type natriuretic peptide (BNP) from the ventricles.  

The kidney secretes two hormones: erythropoietin (EPO) which increase the production of red blood cells and calcitriol (active vitamin D3) which promotes the absorption of Ca and its release from the bones.

Covalent bond is the correct answer