Selective deficiencies of pituitary hormones may represent an early stage in the development of more generalized hypopituitarism Generalized Hypopituitarism Generalized hypopituitarism refers to endocrine deficiency syndromes due to partial or complete loss of anterior lobe pituitary function. Various clinical features occur depending on the specific... read more . Patients must be observed for signs of other pituitary hormone deficiencies, and sellar imaging should be done at intervals to check for signs of a pituitary tumor.
(Pituitary structure and function and relationships between the hypothalamus and the pituitary gland are discussed in Overview of the Endocrine System Overview of the Endocrine System The endocrine system coordinates functioning between different organs through hormones, which are chemicals released into the bloodstream from specific types of cells within endocrine (ductless)... read more .)
Isolated growth hormone (GH) deficiency is responsible for many cases of pituitary short stature Growth Hormone Deficiency in Children Growth hormone deficiency is the most common pituitary hormone deficiency in children and can be isolated or accompanied by deficiency of other pituitary hormones. Growth hormone deficiency... read more . Although one autosomal dominant form of complete GH deficiency is associated with a deletion of the GH structural gene, such gene defects probably account for a minority of cases. Treatment of GH deficiency in adults is discussed elsewhere (see generalized hypopituitarism Generalized Hypopituitarism Generalized hypopituitarism refers to endocrine deficiency syndromes due to partial or complete loss of anterior lobe pituitary function. Various clinical features occur depending on the specific... read more ).
Isolated gonadotropin deficiency occurs in both sexes and must be distinguished from primary hypogonadism; men have low serum testosterone levels and infertility, and women have amenorrhea, low serum estrogen levels, and infertility. A eunuchoid habitus (tall, thin, and with long arms and legs) is generally present. However, patients with primary hypogonadism Etiology Hypogonadism is defined as testosterone deficiency with associated symptoms or signs, deficiency of spermatozoa production, or both. It may result from a disorder of the testes (primary hypogonadism)... read more have elevated levels of luteinizing hormone (LH) and follicle-stimulating hormone (FSH), whereas those with gonadotropin deficiency, either secondary (pituitary) or tertiary (hypothalamic), have low-normal, low, or unmeasurable levels of LH and FSH. Although most cases of hypogonadotropic hypogonadism involve deficiencies of both LH and FSH, in rare cases the secretion of only one is impaired. Isolated gonadotropin deficiency must also be distinguished from hypogonadotropic amenorrhea Amenorrhea Amenorrhea (the absence of menstruation) can be primary or secondary. Primary amenorrhea is failure of menses to occur by age 15 years in patients with normal growth and secondary sexual characteristics... read more secondary to exercise, diet, or mental stress. Although the history may be helpful, differential diagnosis may be impossible.
In Kallmann syndrome Secondary hypogonadism , the specific lack of gonadotropin-releasing hormone (GnRH) is associated with midline facial defects, including anosmia and cleft lip or palate, and with color blindness. Embryologic studies have shown that GnRH neurons originally develop in the epithelium of the olfactory placode and migrate into the septal-preoptic region of the hypothalamus early in development. In at least some cases, gene defects, localized to the X chromosome in the X-linked form of the disorder and termed the KALIG-1(Kallmann syndrome interval gene 1) gene, have been found in the adhesion proteins facilitating this neuronal migration. Administration of GnRH is not indicated.
Isolated adrenocorticotropic hormone (ACTH) deficiency Secondary Adrenal Insufficiency Secondary adrenal insufficiency is adrenal hypofunction due to a lack of adrenocorticotropic hormone (ACTH). Symptoms are the same as for Addison disease and include fatigue, weakness, weight... read more is rare. Weakness, hypoglycemia, weight loss, and decreased axillary and pubic hair suggest the diagnosis. Blood and urinary steroid levels are low and rise to normal after ACTH replacement. Clinical and laboratory evidence of other hormonal deficiencies is absent. Treatment is with cortisol replacement, as for Addison disease Treatment Addison disease is an insidious, usually progressive hypofunctioning of the adrenal cortex. It causes various symptoms, including hypotension and hyperpigmentation, and can lead to adrenal crisis... read more ; mineralocorticoid replacement is not required.
Isolated thyroid-stimulating hormone (TSH) deficiency Hypothyroidism Hypothyroidism is thyroid hormone deficiency. Symptoms include cold intolerance, fatigue, and weight gain. Signs may include a typical facial appearance, hoarse slow speech, and dry skin. Diagnosis... read more is likely when clinical features of hypothyroidism exist, serum TSH levels are low or not elevated, and no other pituitary hormone deficiencies exist. Serum TSH levels, as measured by immunoassay, are not always lower than normal, suggesting that the TSH secreted is biologically inactive. Administration of recombinant human TSH increases thyroid hormone levels.
Isolated prolactin deficiency has been noted rarely in women who fail to lactate after delivery. Basal prolactin levels are low and do not increase in response to provocative stimuli, such as thyroid-releasing hormone. Administration of prolactin is not indicated.