Answer: All the given options serve endocrine functions.
Step-by-step explanation:
Skin is the endocrine gland organ which helps in the production of vitamins. And the cholesterol present in the epidermis are exposed in the ultraviolet radiation and then it enters into the blood.
Small intestine function is that, the endocrine cells of the GI tract are present in mucosa. And it performed stimulation in gastrin and released of the hydrochloric acids. Secretin hormone stimulate from the pancreas and release bicarbonate.
Adipocytes are the cells of adipose tissue and secrete hormones are involved in storage and lipid metabolism.
Therefore, all of the above serve endocrine functions.