Apart from thyroid cells NIS can also be found, although less expressed, in other tissues such as the salivary glands, the gastric mucosa, the kidney, the placenta, the ovaries and the mammary glands during pregnancy and lactation. NIS expression in the mammary glands is quite a relevant fact since the regulation of iodide absorption and its presence in the breast milk is the main source of iodine for a newborn. Note that the regulation of NIS expression in thyroid is done by the thyroid-stimulating hormone (TSH), whereas in breast is done by a combination of three molecules: prolactin, oxytocin and β-estradiol.