In Turner syndrome one X chromosome is missing entirely or in part, and that loss occurs in roughly one in every 2,500 births of baby girls. The most visible consequence during childhood is short stature, and it does not yield to better nutrition or to an easily replaced hormone: it stems from the absence of a complete copy of the SHOX gene, which is involved in the growth of the long bones. Add to that the missing pubertal growth spurt and early ovarian failure. For decades, recombinant growth hormone has been the standard treatment, and it adds around 5 to 8 centimetres to adult height.
Not every patient responds in the same way, however, and the question many families ask — will my daughter grow like the others? — has driven the search for factors that can anticipate that response. A review published in Endocrinología, Diabetes y Nutrición examines precisely whether the karyotype, the chromosome map that defines each case, can predict it. Its authors look at four scenarios: 45,X monosomy, mosaicism, isochromosome Xq and ring X chromosome.
The pattern they describe is partly intuitive and partly not. Patients with 45,X monosomy usually start off responding well: they grow during the early years, but their growth velocity slows sooner. Those with mosaicism, that is, a mixture of cell lines in which some keep a complete X, hold on to better long-term outcomes. And structural variants involving loss of material from the short arm of the X (Xp) behave much like monosomy, with a similarly attenuated response. The dose of missing X genes leaves, in other words, a measurable mark on the first stretch of treatment.
The second half of the message is the one that matters most to families: over time, those differences between cytogenetic subtypes tend to fade. When final height is the outcome of interest, other variables that can actually be acted upon carry far more weight. The age at which treatment starts, how long it is maintained and, above all, when puberty is induced with oestrogens have a greater impact than the starting chromosome formula. The reason is physiological: oestrogens contribute to closing the growth plates, so the moment they are introduced determines how much active growth remains. Starting them too early, or delaying them with no control, can cost or waste centimetres.
The practical takeaway is not that the karyotype is irrelevant, but that it should not be read as a destiny. A cytogenetic diagnosis informs the associated risks (cardiac, thyroid, metabolic) and helps plan follow-up, yet it does not justify fixed expectations about height. What makes the difference is starting early, sustaining adherence to daily injections, coordinating the handover to adult endocrinology and tailoring the timing of puberty case by case.
It is worth remembering that this is a review, not a trial with new patients, and that its conclusions summarise group trends: within each cytogenetic subtype variability is enormous. Factors such as birth weight, nutritional status, other associated conditions or the individual response to the hormone itself account for much of the final height. That is why the authors stress personalised follow-up and revisiting growth targets throughout treatment rather than fixing them once and for all at the start.
Source: Growth hormone therapy in Turner syndrome: Do cytogenetic subtypes influence outcomes?. Herșcovici II, Cristina Pânzaru M, Constantinescu G, Leuștean L, Ungureanu MC, Preda C, Rusu C. Endocrinología, Diabetes y Nutrición (English ed.) 2026;73(8):501821. DOI: 10.1016/j.endien.2026.501821.
Publication record: https://doi.org/10.1016/j.endien.2026.501821 · PubMed: PMID 42887929
