Hypopituitarism (Simon-Sihan syndrome) is a clinical syndrome that presents with inadequate secretion of adenohypophyseal hormones due to multiple etiologies, secondary to hypogonadal, thyroid, and adrenocortical function. In Silhan syndrome, the gonads are hypogonadal and the ovaries are significantly reduced in women. The uterus and mammary glands are atrophied. Dramatic reduction in the secretion of various hormones due to adenopituitarism, insufficient secretion of thyroid hormones, adrenocortical hormones, and sex hormones. During pregnancy, the pituitary gland is hyperplastic and hypertrophied, and the oxygen demand increases, reaching a peak during delivery, as a special sensitivity to hypoxia. After delivery, the pituitary gland rapidly recovers, blood flow decreases, and the corresponding secretion of various hormones also rapidly decreases. If hemorrhage occurs during childbirth, causing hemorrhagic shock, reduction or disconnection of peripheral blood supply, degeneration of pituitary tissue cells, causing a drastic reduction of various hormones secreted by the pituitary gland and the target organs it innervates, resulting in premature degeneration of the functions of the target organs for various hormones and causing a series of syndromes. The pathological changes of hypopituitarism vary depending on the degree of postpartum hemorrhage and the duration of the disease. Early lesions are hemorrhagic, degenerative, and necrotic. Late lesions are fibrous tissue hyperplasia, or a few cystic epithelial cells remain. The thyroid gland, adrenal cortex, and ovaries are significantly atrophied. The thyroid gland has few follicles, flattened epithelial cells, and thinning of the adrenal cortex fasciculus and reticular zone. The ovaries show only a few primary follicles and white bodies, and the ovulation-free uterus is atrophied, with a thin muscle wall, thin endothelium, few glands, and interstitial fibroplasia, and the rest of the organs have varying degrees of atrophy. The pituitary gland is located in the pterygoid saddle, adjacent to the base of the third ventricle, the lower thalamus and the optic cross, and the lower pterygoid sinus, flanked by the cavernous sinus, the internal jugular vein and 3, 4, 5 and 6 pairs of cerebral nerves. The pituitary gland is composed of two main parts: the adenohypophysis and the pituitary gland, both of which have endocrine functions. The pituitary gland is known to secrete thyrotropic hormone (TSH), adrenocorticotropic hormone (ACTH), growth hormone (GH), luteinizing hormone (LH), follicle stimulating hormone (FSH), prolactin (PRL), human melanocyte stimulating hormone (MSH), and a variety of active peptides. In adults, the pituitary gland weighs 0.6-0.8 g. During pregnancy, the pituitary gland becomes hypertrophic and increases in size by 20%-40%, with a weight of up to 1.0-1.2 g. Hormones secreted by the pituitary gland, such as lactogen, thyrotropin, adrenocorticotropic hormone, and melanocyte hormone, are increased in the bloodstream without any change in the pituitary gland-produced systolic hormone and pressor hormone. Due to the enlargement of the pituitary gland during pregnancy, the oxygen demand of the pituitary gland increases and reaches a peak during labor, so it is particularly sensitive to hypoxia. After delivery, as the fetal placenta is expelled from the body, the concentration of various hormones secreted by the placenta in the blood suddenly decreases, the pituitary gland rapidly replaces itself, and blood flow decreases. At this time, if hemorrhage occurs, hemorrhagic shock occurs. As the pituitary gland is directly supplied by arteries, while the adenopituitary gland relies on the pituitary portal system for blood supply, the blood flow to the pituitary gland is sharply reduced in the event of hemorrhage, and ischemic necrosis is very likely to occur. When postpartum hemorrhage occurs and shock occurs, the sympathetic nerves reflexively glad to cause arterial spasm contraction or even occlusion, so that the pituitary blood supply is significantly reduced or even cut off, and thrombus formation, resulting in a significant reduction in the supply of adenopituitary blood and hypothalamic hormones, if the blood supply is not restored in time, the adenopituitary ischemic necrosis and loss of function.