Genetic factors cause clefts in 20% to 50% of the cases and the remaining clefts are attributable to either environmental factors (such as teratogens) or gene-environment interactions. The polygenic/multifactorial inheritance model predicts that most individuals will be born without clefts; however with a number of genetic or environmental factors, it can result in cleft formation.The development of the face is coordinated by complex morphogenetic events and rapid proliferative expansion, and is thus highly susceptible to environmental and genetic factors, rationalising the high incidence of facial malformations. During the first six to eight weeks of pregnancy, the shape of the embryos head is formed. Five primitive tissue lobes grow:

If these tissues fail to meet, a gap appears where the tissues should have joined (fused). This may happen in any single joining site, or simultaneously in several or all of them. The resulting birth defect reflects the locations and severity of individual fusion failures (e.g., from a small lip or palate fissure up to a completely malformed face). The upper lip is formed earlier than the palate, from the first three lobes named a to c above. Formation of the palate is the last step in joining the five embryonic facial lobes, and involves the back portions of the lobes b and c. These back portions are called palatal shelves, which grow towards each other until they fuse in the middle. This process is very vulnerable to multiple toxic substances, environmental pollutants, and nutritional imbalance.
However, other thyroid diseases such as multinodular goitre, Hashimoto thyroiditis, thyroid adenoma, and thyroid carcinoma also retains the radiotracer because of high metabolic nature of these diseases. Thus, the final diagnosis always requires pathological examination of the tissue in question. Treatment
Parathyroid carcinoma is sometimes diagnosed during surgery for primary hyperparathyroidism. If the surgeon suspects carcinoma based on severity or invasion of surrounding tissues by a firm parathyroid tumor, aggressive excision is performed, including the thyroid and surrounding tissues as necessary.Agents such as calcimimetics (for example, cinacalcet) are used to mimic calcium and are able to activate the parathyroid calcium-sensing receptor (making the parathyroid gland "think" we have more calcium than we actually do), therefore lowering the calcium level, in an attempt to decrease the hypercalcemia. References
External links
Parathyroid cancer entry in the public domain NCI Dictionary of Cancer Terms
Parathyroid Carcinoma (Medscape eMedicine)
Cancer Management Handbook: Thyroid and Parathyroid Cancers
 This article incorporates public domain material from the U.S. National Cancer Institute document: "Dictionary of Cancer Terms".