Partial (selective) deficiency of pituitary hormones

Partial pituitary hormone deficiency may be an early sign of more generalized pituitary pathology. Patients should be evaluated for other pituitary hormone deficiencies, and imaging should include examination of the sella turcica at appropriate intervals to detect a pituitary tumor.

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Forms

Isolated growth hormone deficiency

Isolated growth hormone (GH) deficiency is responsible for many cases of pituitary dwarfism. Although there are isolated cases of autosomal dominant inheritance of complete GH deficiency due to damage to the structural GH gene, such gene defects probably account for a minimal number of cases.

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Isolated gonadotropin deficiency

Isolated gonadotropin deficiency occurs in both sexes and should be differentiated from primary hypogonadism. As a rule, patients have a eunuchoid body type. Patients with primary hypogonadism have elevated levels of luteinizing hormone (LH) and follicle-stimulating hormone (FSH), whereas the levels of these hormones in gonadotropin deficiency are at the lower limit of normal, low, or not measurable at all. Although most cases of hypogonadotropic hypogonadism include deficiency of both LH and FSH, in rare cases the secretion of only one of them is impaired. Isolated gonadotropin deficiency should be differentiated from secondary hypogonadotropic amenorrhea, which develops as a result of physical overload, dietary disorders, or neuropsychiatric stress. And, although clarification of the anamnesis in both cases can help in establishing the diagnosis, in some cases the differential diagnosis can be difficult.

Specific gonadotropin-releasing hormone deficiency

In Kallmann syndrome, a specific deficiency of gonadotropin-releasing hormone (GnRH) is associated with midline facial defects including anosmia and cleft lip or palate, and loss of color vision. Embryologic studies have shown that GnRH-producing neurons develop in a specific manner in the epithelium of the olfactory placode [a localized thickening of the embryonic nutrient layer that forms primordial cell clusters from which cellular structures develop and then migrate to the septal-preoptic area of the hypothalamus early in their development. At least a few cases of the X-linked form of the disease have been found to have defects in a gene located on the X chromosome called KALIG-1 (Kallmann syndrome interval gene 1), which codes for adhesion proteins that facilitate neuronal migration. Gonadotropin-releasing hormone therapy is not indicated in this case.

Isolated ACTH deficiency

Isolated ACTH deficiency is rare. Weakness, hypoglycemia, weight loss, and decreased axillary and pubic hair suggest the diagnosis. Low plasma and urinary steroid hormone levels are found, which return to normal only with ACTH treatment. There are no clinical or laboratory signs of other hormone deficiencies. Treatment is cortisol replacement therapy, as in Addison's disease.

Isolated deficiency of thyroid stimulating hormone of the pituitary gland

Isolated deficiency of pituitary thyroid-stimulating hormone (TSH) is likely when clinical features of hypothyroidism are present, plasma TSH levels are not elevated, and there is no deficiency of other pituitary hormones. Plasma TSH levels measured by enzyme immunoassay are not always below normal, indicating that TSH secretion is biologically inactive.

Isolated prolactin deficiency

Isolated prolactin deficiency is rare in women who stop lactating after delivery. Low prolactin levels are recorded that do not increase after stimulation (provocation tests), such as the thyrotropin-releasing hormone test. Prescription of prolactin is not indicated in this case.