Embryology, anatomy, physiology, and normal and abnormal radiopharmaceutical concentration in the pituitary gland: An educational exhibit

Introduction: The number of radiopharmaceuticals (RPs) used in Nuclear Medicine (NM) is increasing. The pituitary gland is often in the field of view of NM images. Hence it is important to be aware of physiologic concentration of various RP in the pituitary gland and as well as correctly identifying abnormal RP uptake in pathologic conditions. The complex embryology, anatomy and physiology of the pituitary plays an important role in the concentration of various RPs in the pituitary.

This exhibit will concisely review embryology, anatomy and physiology of the pituitary gland and normal and abnormal concentration of various RPs used in NM.

Methods: A brief pictorial account of embryology, anatomy and physiology of the pituitary will be discussed. Review of incidentally found RP concentration in the pituitary in planar images, SPECT and PET/CT in our institution with representative images will be given. In addition, RP concentration seen in the pituitary in the literature will be listed.

Results: The pituitary is an amalgam of two tissues. The ectoderm of Rathke’s pouch contributes to anterior pituitary (adenohypophysis)and the ectoderm of the diencephalon of the brain develops into posterior pituitary (neurohypophysis). Most of the pituitary is outside the dura, except the superior part which is surrounded by dura. Pituitary gland is not protected by the blood bran barrier and hormones produced by pituitary are secreted directly in the blood. The infundibular stalk, a part of the neurohypophysis, is covered by the pars tuberalis, a part of the adenohypophysis. The neurohypophysis produces antidiuretic hormone and oxytocin. The adenohypophysis produces growth hormone, TSH, ACTH, FSH, LH, Endorphin, enkephalin and beta melanocyte stimulating hormone.

Physiologic concentration: RPs that are somatostatin analogs such as In-111 Octreotide, Ga68 DOTATATE, Cu64 DOTATATE and Lu177 DOTATATE show physiologic uptake. In adenomas the uptake is increased. Physiologic uptake of FDG, Fluciclovine in the pituitary is variable.

Pathologic conditions: FDG, Axumin, PSMA based RPs, TC-99m Folate and Tc-99m MBI may demonstrate increased uptake in pituitary tumors.

Conclusions: The aim of this exhibit is to provide a concise review of embryology, physiology, and anatomy of the pituitary gland. A list of RPs that show physiological or pathological uptake are provided.

• Download figure
• Open in new tab
• Download powerpoint