In males a pair of testis is present in the scrotal sac. Testes perform dual functions as a primary sex organ as well as an endocrine gland. This gland is absent in females. In females a pair of ovaries is present which are located in the abdomen. Ovary is the primary female sex organ which produces ovum during menstrual cycle and act as an endocrine gland in producing hormone like estrogen and progesterone. This gland is absent in males.

Zona glomerulosa (outer layer) envelops zona reticularis (inner layer) from the outside.

Erythropoiesis is the process of formation of RBC. Peptide hormone erythropoietin secreted from the juxtaglomerular cells of kidney stimulates erythropoiesis.

Pars intermedia of pituitary gland secretes only one hormone called Melanocyte Stimulating Hormone (MSH). This hormone causes dispersal of pigment granules in the pigment cells, thereby darkening the colour in certain animals like fishes and amphibians.

Calcitonin/thyrocalcitonin is a 32 amino acid, linear polypeptide hormone that is produced in humans primarily by the parafollicular cells of the thyroid gland. It checks excess $\mathrm{Ca}^{2+}$ and phosphate in plasma by decreasing mobilisation from bones. Deficiency of calcitonin results in osteoporesis or loss of bone density (due to dissolution of parathormone).