Clinical Description
PROP1-related combined pituitary hormone deficiency (CPHD) is associated with deficiencies of: growth hormone (GH); thyroid-stimulating hormone (TSH); the two gonadotropins, luteinizing hormone (LH) and follicle-stimulating hormone (FSH); prolactin (PrL); and adrenocorticotropic hormone (ACTH). The secretion of all these pituitary-derived hormones declines gradually with age; often the order of appearance of hormone deficiency is GH, LH and FSH, TSH, and then ACTH. The degree of hormone deficiency and the age of onset of the deficiency are variable even within the same family. To date, hundreds of individuals have been identified with PROP1-related CPHD [Baş et al 2015, Fritez et al 2015, Rohayem et al 2016, Madeira et al 2017, Gorar et al 2018, Bajuk Studen et al 2019, Correa et al 2019, Bulut et al 2020]. The following description of the phenotypic features associated with this condition is based on reports that included affected adults to account for the later onset of gonadotropin and ACTH deficiency.
GH deficiency. In general, short stature is the first symptom reported in individuals with PROP1-related CPHD. Most affected children have normal birth weight and birth length and an uncomplicated perinatal period. Hypoglycemia in newborns with PROP1-related CPHD may rarely occur. Growth deficiency with moderate-to-severe growth deceleration usually develops within the first year of life (height -1.5±0.9 SDs at age 1.5 years) and becomes more prominent later in infancy and early childhood, mainly between ages 1.5 and 3 years (-3.6±1.3 SDs at age 3 years), when parents seek medical assistance. At diagnosis, bone age is usually severely delayed (-4.0 SDs at age 2.5 years) and hands and feet are proportionately small.
Clinical response to exogenous GH usually depends on the severity of GH deficiency, deficiencies of other pituitary hormones, age of onset of growth failure, the time interval between the onset of growth failure and the onset of GH therapy, duration of replacement therapy, and the sex of the affected individual.
If treatment is started early in life, GH therapy is very effective for linear growth to achieve familial expected height. GH therapy has also improved body composition and quality of life in older individuals [Doknic et al 2020].
TSH deficiency. Rarely, hypothyroidism is the presenting finding. Hypothyroidism is usually mild and occurs in later infancy and childhood. Since it is usually not congenital or severe, it is not associated with intellectual disability or other physical findings of congenital hypothyroidism. TSH deficiency can be present in individuals with apparently normal TSH-T4 axis.
FSH and LH deficiency. Newborn males with early-onset gonadotropin deficiency can present with micropenis (stretched penile length <2.5 cm in a term infant) with or without cryptorchidism.
Affected individuals with later onset can have absent or delayed and incomplete secondary sexual development and infertility. Adolescent males may present with small penis, small testes, onset of puberty after age 14 years, and/or cessation of secondary sexual development. Adolescent females may present with lack of breast development or delayed menarche. Some females experience menarche before requiring hormone replacement therapy [Flück et al 1998]. Gonadotropic function can also progressively decline and present as primary or secondary lack of reproductive function. There are reports of spontaneous puberty with decline of gonadotropic function in individuals with p.Arg120Cys, p.Phe88Ser, and c.150delA
PROP1 variants. Impaired gonadotropic function occurs in all individuals with the most common PROP1 variant, c.301_302delAG.
Gonadotropin deficiency can be the presenting feature, with GH deficiency and TSH deficiency developing later in adulthood [Reynaud et al 2005].
Prolactin (PrL) deficiency generally causes few symptoms, aside from impaired lactation in adult women [Voutetakis et al 2004].
ACTH deficiency most often occurs in adolescence or adulthood. The range of onset of ACTH deficiency is age 11 years to 63 years. Individuals may present with persistent weakness, abdominal pain, anorexia, and weight loss. Neonatal presentation and signs of acute ACTH deficiency have not been described. It appears unlikely that deficiency of the PROP1 transcription factor causes ACTH deficiency directly, but PROP1 may have some role in differentiation or viability of corticotrophs [Araujo et al 2013]. Surveillance is extremely important in all individuals with PROP1-related CPHD because adrenal function gradually declines over time, even after more than four decades. Furthermore, as GH replacement can increase cortisol metabolism, it is necessary to be aware of the signs of an unveiled adrenal insufficiency.
Intelligence is usually normal.
Other findings
Prevalence
The prevalence of PROP1-related CHPD is estimated at fewer than 1:30,000 individuals, and PROP1 pathogenic variants are the most common cause of CPHD worldwide. PROP1 pathogenic variants were found in 6.7% of simplex cases and 48.5% of individuals with familial CPHD [De Rienzo et al 2015]. Incidence of PROP1 variants in individuals with CHPD varies widely by ethnicity: 70.1% in Lithuania (47/67 individuals with CPHD were found to have biallelic PROP1 pathogenic variants); approximately 53% in the Brazilian population (16/30 individuals tested), 50.8% in Poland (32/63); 0% in the Netherlands (0/50), the United Kingdom (0/27), Japan (0/71), Korea (0/12), and Australia (0/33).
PROP1-related CHPD may be more common in populations with reported founder variants (see Table 7).